Check In and Safety... 4

Transcription

1 Table f Cntents Check In and Safety... 4 Lab Drawer Equipment... 4 Safety Statement... 5 Safety Quiz... 7 Exercise 1A: Math Basics... 9 Exercise 1B: Dimensinal Analysis Experiment 2: A Penny fr Yur Thught; Scientific Methd Intrductin Objective Materials Intrductin Prcedure Part I Experiment 2: Data Sheets Prcedure Part II Data Sheets - Part II Experiment 3: Measurements, the Metric System & Density Objective Materials Intrductin Prcedure Experiment 3: Data Sheets Experiment: Energy f Fd Objective Materials Intrductin Prcedure Experiment 4: Data Sheets Exercise 6A: Naming Cmpunds Exercise 6B: Lewis Structures & VSEPR Experiment: Separatin f a Ternary Mixture Objective Materials Intrductin

2 Prcedure Experiment 7: Data Sheets Exercise 8A: Balancing Chemical Equatins Exercise 8B: Stichimetry Exercise Experiment: Chemical Reactins & Chemical Equatins Objective Materials Intrductin Prcedure Experiment 9: Data Sheets Pstlab Questins Experiment: The Mle Objective Materials Intrductin Prcedure Experiment: Using Gas Laws t Identify an Unknwn Liquid Objective Materials Intrductin Prcedure Experiment 11: Data Sheets Pstlab Questins Experiment: Cncentratin f a Salt Slutin Objective Materials Intrductin Prcedure Experiment 12: Data Sheets Pstlab Questins Experiment: Intrductin t Equilibrium and LeChatelier s Principle Objective Prcedure Experiment 13: Data Sheets Experiment: Titratin f Vinegar

3 Objective Materials Intrductin Prcedure Experiment 14: Data Sheets Pstlab Questins A. Appendix Cmmn Cnversins Slubility Rules Plyatmic Ins Peridic Table

4 Check In and Safety Lab Drawer Equipment 4

5 Safety Statement The safety f yurself and yur classmates is f paramunt imprtance while in the labratry. In the labratry the chemist wrks with many ptentially dangerus substances and equipment. The mst general rules fr safe labratry peratins are: be alert, stay alert, and take the truble t understand what yu are ding and the ptential hazards assciated with the peratin yu are perfrming. Sme basic rules and precautins are: 1. Always wear safety glasses t prtect yur eyes frm chemicals and brken glassware. 2. Shes cvering the tps f feet must be wrn at all times while in the lab. 3. Never wrk alne in the labratry - anther persn shuld be in the lab rm at all times. 4. Use fume-hd when wrking with pisnus r ffensive gases and fumes, r when cnducting prcedures invlving flames. 5. Never heat rganic slvents (alchl, ether, benzene, etc.) in an pen vessel ver an pen flame. Organic slvents are highly flammable s nly ht plates r a heating mantle shuld be used arund these flammable liquids. 6. Avid pinting the muth f a vessel that is being heated tward any persn, including yurself and the instructr. 7. Never heat chemicals f any kind in a fully clsed system - the system must be pen t air t prevent pressure build-up & explsin. 8. Never add anything (including water) t cncentrated acid - instead slwly add acid t ther substances t avid splashing f acid. 9. Lubricate glass tubes & thermmeters with glycerl then hld with a twel r thick glves when pushing thrugh a rubber stpper. 10. Never pipet anything by muth - especially txic r crrsive substances. 11. Immediately sweep up spill taking place n the balance. Clean up all spills immediately, even thse ccurring n yur lab bench. 12. Be sure t label all chemical cntainers crrectly. 13. D nt perfrm any unauthrized experiments. 14. Beware f ht glass tubing - glassware lks cl lng befre it can be handled safely. 15. Never thrw matches, litmus, r any insluble slids in the sink. 16. Avid using excessive amunts f reagents - 1 t 3 ml is usually ample fr test tube reactins. 17. D nt lay dwn the bttle stppers. Impurities may be picked up and cntaminate the slutin when the stpper is returned. 5

6 18. D nt heat thick glassware such as vlumetric flasks, graduated cylinders, r bttles; they break easily with heat. Always check glassware fr stress and fatigue such as stars and cracks befre using. D nt use these pieces f glassware. 19. Never pur anything back int a reagent stck bttle - take ut nly the amunt that will be used. 20. Tie back lng hair and refrain frm wearing flwing, fluffy clthing - bth are fire hazards in the labratry. 21. Knw the lcatin f exits, fire extinguishers, eye washers, first aid kits, the fire blanket & ther safety devices in the labratry. 22. De-inized water may be btained thrugh the curved faucet f each sink. The faucet perated by the ft pedal is the tap water. (Generally, it is gd lab technique t d a final rinse with de-inized water when cleaning glassware.) 23. Never use the thermmeter as a stirrer. Yu may break the thermmeter and in sme cases, release txic mercury. 24. N eating, drinking r chewing gum in the lab whatsever. If yu need t eat r take a swig f water, step utside f the lab and d s. Safety regulatins must always be bserved as it nly takes ne accident t cause blindness r serius permanent injury. Safety glasses must be wrn at all times. After the first day f lab a 50% penalty will be assessed t yur safety quiz if yu cme t lab withut yur safety glasses. If yu remve yur safety glasses when lab is being cnducted yur instructr will give yu a verbal warning nce, the secnd time 10 pints will be reduced frm yur lab reprt, and a third ffense will result in dismissal frm lab. Initials SAFETY STATEMENT: I am aware that there are hazards assciated with being in a chemistry labratry. I have been made aware f the safety equipment available in the labratry rm and hw it is t be used. I have als been made aware f sme cmmn hazardus such as: brken glass fire, acids, bases, and the pisnus nature f mst chemicals. I will always wear my safety glasses during lab. I understand that special precautins fr individual experiments will appear in the lab manual in a sectin entitled "Safety". (Please sign belw). Signature Date Print name (CSID) Cllege Student ID Number 6

7 Safety Quiz Name last: First / Scre Chemistry 100L Date Indicate in the space prvided whether each f the fllwing lab safety statements is True (T) r false (F). 1 Students must purchase and use prtectin eyewear when cnducting experiments. These eyewear must meet the standards f the American Natinal Standards Institute fr "Practice fr Occupatinal and Educatinal Eye and Face Prtectin" (ANZI Z87.1). Safety eyewear cannt be remved until the whle class is dne with the experiment and all chemical and equipment are put away. Only when it is safe will the instructr must give permissin fr students t remve their safety gggles. 2 Befre wrking n an experiment, students must knw the lcatin f the fire extinguisher, first-aid kit, eye wash statin, emergency call bx, safety shwer, and ther safety equipment in the labratry. 3 It is kay t eat r drink in the lab during the prelab discussin but it is never permissible t smke in class. 4 It is never permissible t taste chemicals in the lab. All chemicals are t be cnsidered hazardus unless instructed therwise. 5 Wafting is a technique t smell gas, by placing the drus material directly under yur nse. 6 If any chemicals cntact yur skin r eyes, flush immediately with water, and then ntify the instructr. 7 Althugh mst rules indicate yu shuld never place material frm the labratry int yur muth, there are sme exceptins that allw sme materials t be place in yur muth such as using a pipet. 8 Perfrm all reactins that invlve gases with an unpleasant dr under a fume hd. 9 When heating a test tube, make sure the test tube is cmpletely clsed s that nthing spills. 10 Thick, heavy glves shuld be used, and glassware shuld be lubricated with glycerl r water when inserting glass tubing (i.e., thermmeter) int a stpper. 11 It is kay t perfrm unauthrized experiments. 12 Immediately sweep and clean Balances/Scales after use. In ther wrds, the next persn t use the balance (r scale) is nt respnsible fr yur mess. 13 It is kay t dispse f all slutins including all rganic chemicals dwn the sink. 14 Pur acids int water (nt water int acid) because the heat release will be absrb by the water s that splattering is avided. 15 It is kay t disregard the special safety precautins mentined in each experiment. 7

8 16 Wear clsed-te shes at all times in the labratry. 17 If glassware breaks while in use, it is kay t leave it alne, nt clean it up, and nt tell anyne. 18 Read all parts f an experiment (Objectives, Discussin, Prcedure, & Pre-lab Assignment), befre perfrming each lab. 19 It is kay t take an excess amunt f chemicals fr an experimental prcedure. If the chemical is unused, it can always be returned back t the riginal stck cntainer. 20 An imprtant general rule when perfrming experiments in the labratry is t be alert, stay alert, and take the truble t understand the ptential hazard assciated with each experiment. 21 It is kay t heat rganic slvents directly ver a Bunsen burner rather than a ht plate. 22 All glassware shuld be inspected fr stars, cracks, r stress befre usage and especially befre heating. 23 It is permissible t place chemicals directly n the metal platfrm f the balance pan when using the balance scale. 24 When an experiment calls fr water, use distilled r deinized water. Use tap water first t clean the glassware and then d a final rinse with distilled r deinized water. 25 Befre leaving the labratry, all cmmunity lab equipment is t be returned t its riginal place, i.e. ring stand t lcatin under hds; all excess slid chemical waste shuld be placed in a designated waste cntainer; each labratry statin shuld be straightened-ut with chairs pushed in; and students shuld wash their hands. This quiz is yur cntract that yu will abide by all safety rules f the labratry. Failure t cmply will reduce yur grade n this quiz, and may result in being asked t leave the labratry if yur safety r the safety f thers is at risk. Initials 8

9 Exercise 1A: Math Basics Last Name First Lab Partner(s): / pts Day aaaa. pppp. Answer all questins with the crrect number f significant figures. I. Runding ff Numbers. a. Rund t the tenth place: = b. Rund t the thusandths place: = c. Rund t the tenth place: = d. Rund t the hundredth place: = e. Rund t the ten-thusandths place: = II. Significant figures. Write the number f significant figures fr each f the numbers belw. a b. 970 c d e f g. 904 h i j III. Scientific Ntatin. Rewrite the numbers belw in scientific ntatin. a. 5 b c. 7,100 d. 600,600,000 e. 67,000 f g h i j. 1,106,140,000 9

10 IV. Math peratins using significant figures. Answer the fllwing using the crrect number f significant figures. Fr each, write the raw answer first then rewrite the runded-ff answer in the parenthesis. Use scientific ntatin where apprpriate. a = ( 5.9x 10 0 ) b = ( ) c = ( ) d = ( ) e = ( ) f = ( ) g = ( ) h = ( ) i = ( ) j = ( ) V Math peratins using pwer-f-ten: Calculate each and write yur answers in scientific ntatin. a = b. ( ) ( ) = c. 2.0 xx xx10 1 = d = e. ( ) (10 1) = f = g. ( ) + ( ) = *HINT: Answers c & d shuld be different. Answers e & f shuld be the same. 10

11 Exercise 1B: Dimensinal Analysis Last Name First Lab Partner(s): / pts Day aaaa. pppp. Write all answers with the crrect number f significant figures and the crrect units. 1. Determine the fllwing cnversin factrs. Use nly the cnversins fund in the appendix and write yur answers t at least 3 significant figures. a lb = g b lb = kg c z = g d qt = ml e qt = L f gal = L g in = cm h m = in i cup = ml j fl. z = ml 2. Answer the fllwing using dimensinal analysis. a. Hw many kilgrams in lb? b. Hw lng in centimeter is a 30.5-inch waist? 11

12 c1. A Prius autmbile requires 11.9 gallns f gasline (gas) fr a full tank. Hw many ml f gasline is needed fr a full tank in this Prius? c2 Refer t the abve questin. If gasline has a density f 0.75 grams per ml, what is the mass (in grams) f this vlume f gasline? (Remember that 0.75 g/ml is a measured cnversin factr.) d. Hw fast is a car mving in cm / sec if its speedmeter reads mph? e. Hw many pennies are needed (19.5 mm diameter) t stretch frm the earth t the sun? It takes 8.00 minutes and 15.0 secnds fr light t travel frm the sun t the earth traveling at 186,282 mi/sec. Hw much is this many pennies wrth in dllars? 12

13 Experiment 2: A Penny fr Yur Thught; Scientific Methd Intrductin Objective The purpse f this experiment is t familiarize students with the Scientific Methd, t learn t distinguish between chemical and physical prperties, and t learn t write a supprted cnclusin based n their experimental data & bservatins. Students will frm a hypthesis, test it, revise it and test it again. During this prcess students gain familiarity with sme labratry equipment and slutins including balances, rulers and wrking with strng acid in the hd. Critical thinking skills will be develped as the students draw cnclusins frm their data. Materials Pennies frm 1960 present Metric ruler Tngs/frcepts Balance 50 -ml graduated cylinder Shear metal cutter Petri dish 1 M HCl Intrductin Begin by Reading: Ch 1.2 Chemistry in ur Lives Timberlake 5 th Editin. Scientific Methd: Thinking Like a Scientist. Familiarize yurself with Questins 1.7 and 1.9 at the end f this sectin. In additin, read Chapter 2.7 Density & Chapter 3.2 States and Prperties f Matter. Pennies & Mass Fr this experiment, we begin with the questin, What happens t the mass f a cin as it ages? In this experiment a hypthesis is written fr what is expected t happen t the mass f a penny as it ages. The mass may increase with dirt and ils adhering t the surface. It may als wear and lse mass. Yu will be asked t make a predictin. Experiments will fllw that may r may nt supprt yur hypthesis. Physical & Chemical Prperties In the experiments that fllw, yu will be asked t recrd bservatins abut the physical and chemical prperties f pennies. Physical prperties include clr, size, density and hardness. Chemical prperties describe reactivity f a substance, including flammability. In a chemical change, a chemical reactin ccurs and a substance is cnverted int ne r mre new substances. One physical prperty that will be determined is density. DDDDDDDDDDDDDD = mmmmmmmm vvvvvvvvvvvv Cnclusins Yu will be asked t write a cnclusin based n the data and bservatins frm yur experiments. Yu must cite physical prperties and chemical changes in yur cnclusin t supprt it. If yur cnclusin des nt supprt yur hypthesis, yu may need t revise it and design new experiments. 13

14 Prcedure Part I 1 Write a hypthesis using cmplete sentences n hw the mass f a penny changes with age. 2 Srt Pennies. a. Gather the pennies fund at the back statin and srt the pennies based n the year minted. b. Nte the cnditin fr each side f the cin. Place pennies minted prir t 1980 in ne pile and pennies minted between in anther pile and finally, pennies minted after 1983 in the third pile. Keep these piles until the end f the lab. c. Find tw pennies minted in each f the decade 1960's, 70's, 80's... and srt them in increasing rder accrding t the year the cin was minted. Yu may team up with anther grup. 3 Determine the mass f varius pennies. a. Weigh each f the 10 pennies n the scale and recrd the mass in yur datasheet frm ldest t newest. Write the mass and the unit in yur datasheet. Use the frceps (tweezers) when handling the pennies here after. b. Recrd the detailed cnditin fr each f the cin, citing the physical prperties. c. Prepare a graph with prper labels and headings, including units. d. What are the axes labels in the graph? e. Take the infrmatin yu cllected and place a ο fr the mass f each penny with it s year minted. Plt class data as well if it is aggregated. 4 What cnclusin can yu draw frm yur data? Be sure t cite specific evidence frm yur data t supprt yur cnclusin. Use the class result t prvide an verall view f hw the mass f a penny changes with age. Des yur graph shw a gradual increase r decrease f the mass with age? Is smething unexpected fund frm the data? 5 Des yur cnclusin supprt yur hypthesis? Answer this questin in yur data sheet. 14

15 Experiment 2: Data Sheets Last Name First Lab Partner(s): / pts Day aaaa. pppp. Part I 1 Hypthesis: Write a cmplete hypthesis n what yu think happens t the mass f a penny with age? Use cmplete sentences. 2 Mass f Assrted Pennies Use and write the apprpriate units after each data entry. Measure the mass t the precisin f the scale. Measure the diameter and thickness t the hundredth f a centimeter. # Year Mass (g) 1 Oldest Diameter (cm) Thickness (cm) Cnditin f cin Newest 15

16 3 Graph f Mass f the penny vs year minted Mass f Penny vs. Year Minted (Label the graph belw with prper labels) What is yur cnclusin based n the graph generated frm class data? 5 Is yur hypthesis cnsistent with the graph r is there smething unexpected that the graph shws? 16

17 Prcedure Part II 1 Write a hypthesis abut why the pennies mass changes that is cnsistent with the unexpected result fund in the first part f this lab. 2 Determine the Density f the Pennies Trade pennies with anther grup until each grup has 25 pennies all f which are either lder pennies (minted befre 1982) r newer pennies (minted after 1983). a. Take the stack f 25 pre-1982 pennies, place these n the scale and recrd the ttal mass f the 25- pennies. Repeat this fr the newer pennies and recrd the mass. b. Calculate the average mass f the pre and pst pennies by dividing the ttal mass by 25. c. Fill a 100-ml graduated cylinder with water t the 20.0-ml mark. Use a drpper t get the meniscus exactly t 20.0 ml. d. Carefully place 25 pre-1982 pennies int the cylinder. Avid trapping air bubbles under the pennies r splashing water up the sides f the cylinder. e. Accurately measure the ttal vlume f the water and the pennies. Recrd this measurement in yur datasheet. f. Remve the pennies and thrughly dry them with paper twel. Return the dry pennies back t their riginal cntainer. g. Calculate the average vlume f a penny by dividing the vlume f the pennies by 25. Repeat this fr the pst-1982 pennies. h. Calculate the average density f pre 1982 and pst 1982 pennies. 3 Physical Observatins f Appearance a. Take 1 penny minted befre 1981 and 1 penny minted after 1983 and use a metal cutter t cut these pennies in half. (Obtain whichever ne yu dn't have frm anther grup). T save n pennies, yur instructr may demnstrate this part fr yu. b. Examine the interir f the tw half-pennies and recrd yur bservatins in yur datasheet. 4 Chemical Prperties f the Pennies a. Using a frceps take the half f each type and put them in a Petri dish. Place the Petri dish with the pieces f pennies under the hd. b. Add a small amunt f 1 M hydrchlric acid (CAUTION: This is a crrsive liquid) Observe any difference in chemical reactivity between each f the halves fr the tw pennies. Such differences, if they ccur, can be taken as evidence f differences in cmpsitin. T save n pennies, yur instructr may demnstrate this part fr yu. 5 Cnclusins. What cnclusin can yu make base n yur data? Use the evidence in this experiment t supprt yur cnclusin. Write yur answers in cmplete sentences. 6 Draw a flwchart f the scientific methd yu emplyed in this experiment. 17

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19 Data Sheets - Part II Last Name First Lab Partner(s): Day aaaa. pppp. 1. Hypthesis: Write a cmplete hypthesis as t why the weight f a penny changed after State in yur hypthesis what happened t the mass f the penny after a certain year. 2. Density Table f Measured Mass & Vlume f Pennies Penny Type Mass f 25 pennies (t hundredth gram) Vl initial (t tenth ml) Vl final (t tenth ml) Vl f 25 pennies Pre- ' and earlier Pst - ' and later Calculatin f Density - Avg. mass, vlume and density f pre-'82 and pst-'82 pennies. Type f penny Average Vlume Average Mass Density pre pst Calculatins: Shw ne sample calculatin fr the average vlume, average mass and density. 19

20 3. Describe the inside f the pre-1982 and the pst-1982 pennies. 4. Describe yur bservatins f what ccurs when the pre-1982 and the pst-1982 cut pennies are expsed t 1 M HCl. 5. Based n yur Observatins, Experimental Data and Calculatins, write a cnclusin fr Part II f this experiment. Be sure t cite yur data directly t supprt yur cnclusin. 20

21 6. Flwchart Create a flw chart that illustrates hw the scientific methd was used in Part I and Part II. Include details and label each bx with its crrespnding part f the scientific methd. Include bth Parts in yur flwchart. 21

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23 Experiment 3: Measurements, the Metric System & Density Objective The purpse f experiment is t becme familiar with the metric system by taking measurements using metric units. Additinally, the purpse f this experiment is t take measurements using varius measuring devices and then reprt these measurements with the crrect precisin based n the apparatus used. Each measurement will be cnverted t ther units using dimensinal analysis with the answers reprted t the crrect number f significant figures. Materials Alchl Thermmeter Metric Ruler Metallic Cube Unknwn Brand new #2 Pencil Lab Manual 100 and 250 ml beakers Empty 2-L sda bttle with cap 10 ml, 25 ml, 100 ml prefilled with clred liquid 500 ml graduated cylinder Intrductin Additinal Reading: Ch , Chemistry in ur Lives, 5 th Editin Timberlake. Chemistry and Measurements. Fr this experiment, yu will be taking measurements with several different labratry tls. Emphasis in grading will be placed n recrding measurements with prper significant figures and with prper units. 23

24 Prcedure Part I Metric Measurements & Estimates Measuring Temperature Temperature is measured in Celsius r Kelvin in a labratry setting. The lines n the thermmeter represent 0.1 C increments in temperature. Yur recrded measurement f the temperature shuld estimate between the lines and carry with it tw decimal places r precisin t 0.01 C. Fill a 250 ml beaker 1/2 full (125 ml) with tap water and allw it t reach rm temperature, abut 30 minutes. Prceed with ther parts f the labratry while yu wait fr the temperature t equilibrate. Recrd the temperature f the water with the crrect number f significant figures and units. Measuring Mass 1. Measure the mass f the fllwing bjects. Yu must recrd all significant figures frm the balance. This means measurements t g. If the numbers n the scale fluctuate, ask peple t mve away frm the scale and clse the drs t the lab if they are pen. Yur recrded measurement is the midpint f any fluctuatins that cntinue. a. Brand new #2 pencil b. 100 ml r 150 ml beaker c. 2-L sda bttle empty with cap Estimate the mass f yur lab manual. D nt measure it n the scale. Measuring Distance 1. Measure the fllwing lengths, in centimeters, using a meter stick, and recrd the measurements in yur datasheet with the crrect number f significant figures and units. Recrd the measurement nly t the precisin that the instrument allws. On the meter stick the lines represent millimeters r 0.1 cm. Therefre, yur measurements shuld be recrded t the 0.01 cm. a. Yur height in centimeters b. The length f a new pencil c. The circumference f a 2-L bttle Estimate the width f yur lab drawer. D nt measure. Measuring Vlume Fr each f the 3 graduated cylinders, d the fllwing prcedure. 1. Determine the value f each increment in milliliters. 2. Read and recrd the vlume in milliliters fr each f the three graduated cylinders fund at the statins arund the labratry. Recrd the vlume frm the bttm f the meniscus. a. 100 ml graduated cylinder (t nearest 0.1 ml) b. 25 ml graduated cylinder (t nearest 0.1 ml) c. 10 ml graduated cylinder (t nearest 0.01 ml) Estimate the vlume f liquid in the displayed test tube. A meniscus as seen in a burette f clred water. '20.00 ml' is the crrect depth measurement. By PRHaney (Own wrk) [CC BY-SA 3.0 ( es/by-sa/3.0)], via Wikimedia Cmmns By PRHaney (Own wrk) 24

25 Part II Determinatin f Density & Identity f an Unknwn bject. Obtain an unknwn cubic slid frm the instructr labratry table. 1. T determine the density by the direct measurement methd, measure the mass using the labratry scale. Vlume by direct measurement Measure the length, width, and height f the cube in centimeters. Calculate the vlume by multiplying the length x width x height. Recrd yur measurements in yur datasheet and shw yur calculatins. Calculate the density f the cube (Equatin belw) dddddddddddddd = mmmmmmmm vvvvvvvvvvvv Vlume by displacement Take a graduated cylinder and fill it half way t a cnvenient vlume. Read the vlume f the water t the precisin f the graduated cylinder. Slwly slide the cube dwn the graduated cylinder being careful nt t splash the water t the side. Measure the new displaced vlume t the precisin f the graduated cylinder. Using the mass frm step1, calculate the density using this vlume measured by displacement. Recrd yur wrk and data in yur datasheet. Fr the Pst Lab Questins Identify yur unknwn based n the experimental density frm a list f pssible metals. Table f Pssible Unknwns Material Density (g/ml) ALUMINUM 2.70 BRASS 8.00 COPPER 8.90 STEEL 7.59 Calculate the percent errr frm yur experimental density frm the listed density f the metal yu have. eeeeeeeeeeeeeeeeeeeeeeee ttheeeeeeeeeeeeeeeeee % eeeeeeeeee = xx 100 ttheeeeeeeeeeeeeeeeee 25

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27 Experiment 3: Data Sheets Last Name First Lab Partner(s): Part I Metric Measurements & Estimates / pts Day aaaa. pppp. magnitude units Temperature Length magnitude units Mass Brand new #2 pencil 100 ml beaker 2-L sda bttle empty w/ cap Lab Manual * estimate** magnitude units Yur height Brand new #2 pencil Circumference f 2-L bttle Lab Drawer width **estimate** Vlume 10 ml graduated cylinder 25 ml graduated cylinder 100 ml graduated cylinder Displayed test tube **estimate** magnitude units 27

28 Part II Determinatin f Density & Identity f an Unknwn bject. UNKNOWN # Magnitude units Mass Calculatin f Density Direct Vlume Length Width Height Vlume Density Vlume by Displacement Vlume initial Calculatin f Density Vlume Final Vlume Slid Density 28

29 Pst Lab Questins 1. Explain why the tw density values frm yur calculatins might be different. Inspect the number f significant figures fr each measurement and speculate which methd fr the determinatin f the vlume f the cube may be mre precise. 2. Based n the measured densities, identify the metal that yur cube is made f. Calculate the percent errr in yur measurement. Identity f Unknwn % Errr Mass Cnversins. D the fllwing cnversins fr the mass f the pencil. Cnversin factr: Cnversin factr: Cnversin factr: measurement frm part I mg = g g = kg lb = g milligrams kilgrams punds Pencil Beaker Shw yur calculatins fr the pencil with prper units cancellatin. Circle yur answer. 29

30 Length Cnversins. D the fllwing cnversins fr the length f the pencil. Cnversin factr: Cnversin factr: Cnversin factr: measurement frm part I mm = cm m = cm in = cm millimeters meters inches Pencil Circumference 2L bttle Shw yur calculatins with the pencil prper units cancellatin. Circle yur answer. Vlume Cnversins. D the fllwing cnversins fr the mas f the pencil. Cnversin factr: Cnversin factr: measurement frm part I ml = L ml = gal Liters gallns 10 ml graduated cylinder 100 ml graduated cylinder Shw yur calculatins fr the 100 ml graduated cylinder with prper units cancellatin. Circle yur answer. 30

31 Experiment: Energy f Fd Objective The gal f this experiment is t determine the energy cntent in tw types f fd, a nut and a snack fd. Tw trials will be perfrmed n each fd, fr a better statistical sampling f data. The fd will underg cmbustin, and the heat will be captured and quantified by mnitring the melting f ice. Materials Utility Clamp Stirring Rd Small sda can Fd hlder Lighter with wand 100-mL graduated cylinder Ring stand Tngs Fd Samples Intrductin Reading: Ch 3.4 Ch 3.7, Chemistry in ur Lives Timberlake. Matter & Energy. Pay special attentin t the sectins n fd and nutritin and using the Heat f Fusin, which yu will need t calculate the energy transfer frm chemical ptential energy t heat energy. Heat f Fusin In this experiment, yu will ignite a nut and anther type f snack fd, and yu will perfrm 2 trials f each. The heat f the cmbustin f the fd (qfd) will be captured t melt ice (qice) in a sda can. qq ffffffff = qq iiiiii The phase transitin between slid ice t liquid water will be quantified by measuring the mass f the ice that has melted. The heat lst frm chemical ptential energy, becmes heat during cmbustin f the fd is transferred t the ice in a sda can. The heat f fusin fr ice is 8.0 x 10 cal/g f H2O. Therefre, the heat r energy cntent in the fd can be calculated in the fllwing way. qq iiiiii = 80.0 cccccc gg xx gggggggggg iiiiii mmmmmmmmmmmm During a phase transitin, the temperature f the matter des NOT change. Therefre, we d NOT need t accunt fr heat using the equatin q=mc T because the temperature f the water in the sda can remains at a cnstant 0 C, as lng as there is still ice in the can at the end f the experiment. It is imprtant t make sure that st has been remved frm the bttm f the can because it can insulate the can and prevent heat transfer t the ice. It is imprtant t burn the fd fr at least a minute s that the sample size is measureable, and that the flame be near the can. Nutritinal Cntent in Different Fds The nutritinal cntent f fd varies depending upn its cntent f carbhydrate, fat and prtein. Fats have a higher calrie cntent per gram than prtein and carbhydrates (Table 1). After yur trials with the fd, yu ll calculate an average kcal per gram f fd and then cmpare it t the infrmatin n the nutritinal label n the package. Table 1 Fd kcal/g kj/g Carbhydrate 4 17 Fat 9 38 Prtein

32 Prcedure Set up f the Calrimeter 1. Obtain a metal can with the tp cut ff, and the edges flded back s the edges are safe. This apparatus will serve as the calrimeter. If necessary, wipe any carbn depsit (st) ff the bttm f the can using a mist paper twel. The st can insulate the calrimeter s that the heat transfer frm the fd t the ice is nt very efficient. 2. Set up the apparatus as shwn in the frnt desk by the instructr, shwn in figure. Use a large adjustable O-ring clamp t hld the metal can. Psitin the fd hlder (fr hlding the nut) at the base f the ring stand, belw the O- ring hlding the aluminum can calrimeter. 3. Select nuts that are at least 1-gram. Use tw pieces if the sample size is t small. If yu d nt burn enugh material, the heat generated may nt be enugh t melt the ice. 4. Weigh the mass f the hlder and recrd this in the datasheet (1). 5. Add the nut (r nut pieces) n t the hlder and weigh the fd hlder and nuts. Recrd this in yur datasheet (2). 6. Befre beginning yur trial, recrd the mass f yur empty 100-mL graduated cylinder (6). Cmbustin f the fd sample 7. Add crushed-ice t the can s it is at least three-quarter full. Pack the ice t the bttm f the metal-cancalrimeter using the bttm f a 150-mL beaker. Be sure nt t press s hard as t break the beaker. CAUTION: Use ht mitts r glves t prtect yur hands in this prcedure s that if the beaker des crack, yur hands are nt cut. 8. Remve the fd and stand frm under the can and use the lighter t ignite the fd. Once the fd is burning, psitin it s that the tp f the flame just tuches the bttm f the can. The fd shuld burn fr a minimum f 1 minute. Let the fd burn as lng as it has flame. If the flame ges ut befre the nut is cmpletely burned, mve the fd hlder away frm the calrimeter t re-ignite the nut, then replace it under the calrimeter (nly when the nut is burning again shuld yu place it under the calrimeter). CAUTION: The can and ring clamp will be ht. Remember cl bject and ht bjects lk exactly the same s be cautius when handling the hardware. 9. Recrd the mass f the fd sample and hlder after it has finished burning in the datasheet (3). 10. Calculate the mass f the fd that has burned and recrd it in the datasheet (4). 11. Being careful nt t burn yur hands, pur the melted ice ut f the sda can int the pre-weighed graduated cylinder. Yu may use a funnel fr this. D nt allw slid ice t fall int the graduated cylinder. Determine the vlume f the water and recrd it in yur ntebk (5). 32

33 12. Measure and recrd the mass f the water and graduated cylinder directly (7), and subtract yur previusly recrded graduated cylinder mass (6) t determine the mass f the melted water (8) (Shw yur calculatin). 13. Clean any st frm the can with a mist paper twel befre prceeding with the next trial. 14. Repeat the prcedure with the same type f nut fr trial 2. After the secnd trial fr the nut, repeat this prcedure fr 2 trials f ne f the snack fds. Calculatin f Heat per gram f fd. 15. The ttal heat prduced frm burning the fd (9) is calculated using the Heat f Fusin f 80.0 calries per gram f ice melted. Therefre, the calculatin is as fllws: qq iiiiii = 80.0 cccccc gg gggggggggg iiiiii mmmmmmmmmmmm (rrrrrr 8) qq iiiiii = qq ffffffff 16. Heat per gram f fd burned is then calculated by taking the abve ttal heat (9) prduced and dividing by the mass f the fd that burned (4). HHHHHHHH pppppp gggggggg = qq ffffffff MMaaaaaa ffffffff bbbbbbbbbbbb (rrrrrr 4) 17. Fr rw 11, cnvert the heat per gram frm calries per gram t kilcalries per gram. 18. Fr rw 12 in the table, average yur tw trials f the nut int ne number. And average yur tw trials f the same snack fd. Summary f Results - Cmparisn t Snack Fd Label. 19. Transfer yur answer fr Rw 12 t the the Summary f results fr the nut and fr the snack fd. Remember that 1 Calrie = 1 kilcalrie. 20. Using the nutritinal label n the packaging fr the nut and the snack fd, calculate the Cal/g fr each. 21. Calculate the percentage errr frm the label fr each. The theretical value is the Cal/gram calculated frm the nutritinal label. EEEEEEEEEEEEEEEEEEEEEEEE vvvvvvvvvv TTheeeeeeeeeeeeeeeell vvvvvvvvvv % eeeeeeeeee = 100 TTheeeeeeeeeeeeeeeeee vvvvvvvvvv 33

34 Experiment 4: Data Sheets Last Name First Lab Partner(s): Mass f Burned Fd and Mass f Melted Ice : / pts Day aaaa. pppp. Sample Nut Snack Trial 1 Trial 2 Trial 1 Trial 2 1 Initial mass f fd hlder g g g g 2 3 Initial mass f fd and hlder g g g g Remaining mass f fd and hlder g g g g 4 Mass f fd burned g g g g 5 Vlume f water melted ml ml ml ml 6 7 Mass f empty graduated cylinder g g g g Mass f graduated cylinder + water melted g g g g 8 Mass f water melted g g g g Shw calculatins fr 1 sample with prper labels, significant figures and units. Circle answers. 34

35 Calculatin f Heat per gram f fd: 9 Heat prduced fr ttal fd ignited: W it t it 10 Heatprduced by 1 gram f fd (cal/g) ignited: 11 Heat prduced by 1 gram fd (kcal/g) ignited: 12 Average heat by 1 gram nut & fd sample (kcal/g) Shw calculatins fr 1 sample with prper labels, significant figures and units. Circle answers. Summary f Results: Cmparisn t Fd Nutritinal Labeling and Percent Errr q Nut Nut Calrie frm package q fd snack Calrie frm package Nut (Cal/g) (Cal / g) % errr Snack Fd (Cal/g) (Cal / g) % errr Shw calculatins fr 1 sample with prper labels, significant figures and units. Circle answers. 35

36 Pstlab Questins: 1. The heat f the cmbusting fd is transferred t the cntents f the can and melts the ice. If yu d nt have enugh ice in the can fr a trial, it will all melt befre the flame extinguishes itself. Once the ice is melted, what des the excess heat f the burning d? Hw can yu quantify this heat? 2. If all f the ice melts when yu were ding this experiment s at the end f the prcedure yu have a calrimeter full f water, hw wuld this affect yur result? Wuld yu calculate a calric value f yur fd t be higher r lwer than the true value? 3. What was yur percent errr fr yur nut and fd sample in terms f calric value? Explain why yur result might be higher r lwer than the nutritinal label (manufacture label). 36

37 Exercise 6A: Naming Cmpunds Last Name First Lab Partner(s): 1. Naming Type I Inic Cmpunds One metal and a nnmetal / pts Day aaaa. pppp. Rb 2 O Al(HSO 4 ) 3 Ca(HCO 3 ) 2 Sr 3 N2 Cd 3 (PO 3 ) 2 2. Naming Type II Inic Cmpunds Cntaining Variable-Charge Metals Cu(C 2 H 3 O 2 ) 2 C2(CO3)3 Hg2S CuO Pb(ClO 3 ) 4 3. Naming Type III - Binary Cmpunds with 2 Nnmetals N2O 2 IF 4 SCl2 SF6 SiO 2 4. Name the fllwing Mixture f Different Types f Cmpunds NaHCO3 NI 3 C2(HPO3)3 NH4ClO4 Pt(CN)2 37

38 5. Frmulas f Type I Inix Cmpunds - One metal and a nnmetal Magnesium chlride Silver sulfite Barium nitrate Aluminum arsenite Beryllium hydrxide 6. Frmulas f Type II Inic Cmpunds - Cntaining Variable Charge Metals Vanadium (III) nitride Chrmium (III) bisulfite Mlybdenum(VI) xide Cpper (II) dichrmate Platinum (IV) perbrmate 7. Frmulas f Type III Cmpunds - Binary Cmpunds with 2 Nnmetals Dinitrgen tetrafluride Dibrn trixide Sulfur hexachlride Dihydrgen mnxide Tetraphsphrus heptaxide 8. Write the frmulas fr the fllwing List f Different Types f Cmpunds. Calcium carbnate Ammnium selenide Cadmium permanganate Thalium(I) telluride Tungsten(V) xalate 38

39 Exercise 6B: Lewis Structures & VSEPR Last Name First / pts Lab Partner(s): Day aaaa. Valence Electrns & Grup Number Element N O P Ca Cl Ga Grup Number # f Valence electrns pppp. Lewis structures Cmpund, Chemical frmula # f Valence electrns # f Nnbnded Electrn pairs n all central atms Lewis Structure Ammnia, NH3 Flurmethane, CH3F Carbn disulfide 39

40 O Frmic acid, HCOOH H C O H Hydrxylamine, NH2OH H H N O H Nitrate in, NOO 3 1 Sulfur dixide Acetate In CH3COO -1 H O H C C O -1 H 40

41 Shapes f Mlecules VSEPR Thery Cmpund # f Valence e- Lewis Structure # f e- Grups # f NnBnded pairs f e- Electrnic Gemetry, Mlecular Gemetry, Bnd angles OF Tetrahedral bent NH3 CH3F CS2 41

42 SiO2 NO 3 NO 2 PI3 42

43 Experiment: Separatin f a Ternary Mixture Objective In this experiment, students create a mixture f 3 substances, idine, sand and cbalt (II) chlride and then separate them using a variety f separatin methds. The gal f this experiment is t familiarize students with the methds f separatin, identify the islated substance at each step and als t identify a physical and chemical changes that may ccur during the separatin f the mixture. Materials Idine crystals Sand Cbalt (II)chlride hexahydrate (CCl2 6H2O) Deinized water Evaprating dish Ht plate Beakers Wash bttle Intrductin The three substances that will be cmpnents in ur hetergeneus mixture have sme unique chemical and physical prperties that will be explited in the prcess f islating each. Here are sme relevant definitins fr this experiment: Sublimatin - the phase change assciated with the transitin frm a slid t a gas withut passing thrugh a liquid. Once cmpund that sublimates at atmspheric pressure is CO2, als knwn as dry ice. Slubility - the ability f a substance t disslve in water, creating an aqueus slutin. When a substance is disslved in water, it s physical state is termed aqueus and is dented (aq). It is NOT in a liquid state. Density Density is mass divided by vlume (g/ml), and it impacts the ability f a substance t sink r flat in a liquid r gas. Vlatility The tendency r ability f a substance t enter the vapr phase. Miscibility The ability f tw liquids t mix hmgeneusly in all prprtins. Water and ethanl are miscible. Islated A substance is islated when it has been remved frm all ther substances. Sugar disslved in water has NOT been islated frm the water. Decantatin The technique f decantatin explits the difference in slubility and density between tw r mre substances fr separatin. In a hetergeneus aqueus mixture, where ne substance is insluble and resting n the bttm f the cntainer, the liquid is pured ut f the cntainer withut transferring the insluble dense substance, which rests n the bttm. Hexahydrate In this experiment, cbalt (II) chlride is seen in tw frms, the anhydrus frm (CCl2) and the hydrated frm (CCl2 6H2O). Bth f these frms f cbalt (II)chlride are slids, but they have a very nticeable difference in physical prperties. Hexahydrate means that there are six waters in the basic frmula f the substance. 43

44 Prcedure Observatin f the Starting material. Obtain three substances, idine (I2), sand (mstly SiO2), and cbalt (II) chlride hexahydrate (CCl2 6H2O), and place these in three small test tubes. In general, measure ut tw crystals f idine abut 1-2 mm in size (tip f spatula). Use an amunt f cbalt(ii) chlride abut 5mm diameter. The amunt f sand shuld be the size f a nickel (1/4 teaspn). Write a descriptin f the appearance f each substance individually. At each stage f the prcedure be sure t identify the islated species and the physical prperty that facilitated the islatin. Recrd by circling and underlining in the Observatins Table. 1. Create the mixture. Thrughly mix tgether the three substances in a 250 ml beaker. Write a descriptin f the appearance f the mixture in yur datasheet in Rw Sublimatin f Substance A. Place crushed ice in an evaprating dish ver the 250ml beaker. Place the beaker with the evaprating dish n a warm ht plate at 3/4-heat setting and bserve the mixture while it is heated. Cntinue t heat the beaker until there is n mre signs f gas in the beaker. If yu still see gas, in the beaker, yu are nt dne. It must be clear and clrless befre yu can prceed t the next step. Observe what happens t all three cmpnents f the mixture. In rder t make careful bservatin, it is best t fllw either idine r the cbalt substance during the heating prcess. Inspect the underside f the evaprating dish during this step. Observatins. When nthing else appears t be happening, remve the beaker frm the ht plate. Be careful that the ice des nt melt t the pint that sme f the ice leaks dwn int the beaker. Allw the beaker t cl fr 2-5 minutes befre handling it. Use ht mitts t remve evaprating dish frm the 250-mL beaker. Pur the water and ice frm the evaprating dish t a 50mL beaker. Place a paper twel n yur lab bench tp and then invert the evaprating dish and place n the paper twel. What is the identity f the residue that accumulated at the bttm f the evaprating dish? Which substance has been islated? Recrd yur answer and bservatin n yur datasheet (in rw 2 if the data sheet table). 3. Disslving substance C. Recrd bservatins f the remaining mixture. Add apprximately 15 ml f water t the 250mL beaker and stir. What is happening? Recrd the clr f the slutin and slid inside this beaker. Write yur bservatin n yur datasheet (rw 3) Nte, that if the clr f the slutin is ther than lavender, i.e., brwn r black, then yu stpped the heating in part 2 prematurely. Yur instructr may ask yu t repeat the prcedure with smaller quantities f idine and cbalt(ii) chlride hexahydrate. 4. Islated substance B via decantatin f C Decant the liquid frm the slid in the 250-mL beaker int a 400mL beaker. Add an additinal 15mL back t the slid residue that remains in the 250mL beaker in rder t wash the slid. Decant the rinse int the 400mL beaker. What substance is separated in this step? What clr is the slid cmpnent? Write yur bservatins in rw 4. 44

45 5. Evaprating water t recver substance C. Put the cntent f the 400 ml beaker n a ht plate. Heat until all the liquid has evaprated. Observe and recrd what happens as the liquid evaprates. Pay clse attentin t the clr change as the last drp f liquid evaprates away. What is the clr f the remaining slid? As sn as the last bit f liquid evaprates turn ff the ht plate and allw the 400mL beaker t cl fr a minute r tw. After recrding yur bservatin, add a small drp f water t the slid, what d yu bserve? Recrd all bservatins frm this step in Rw Cleaning Up. Dispse f substances in waste cntainer and wash all yur glassware. Wipe dwn yur statin. Wash yur hands thrughly with sap and water befre leaving the lab rm. Flwchart f Separatin Scheme I 45

46 46

47 Experiment 7: Data Sheets Last Name First Day / pts Lab Partner(s):. Observatins Table Steps Observatins: Write dwn what is seen in each prcedure. Be as detailed as pssible. State what cmpnent is being islated. Basis f separatin: Circle the basis f separatin. [Slubility, density, vlatility, miscibility, nne] Underline the islated substance (r nne). 1 *Circle the crrect chice [Slubility-density-vlatility-miscibility-nne] -Underline the crrect chice a) Islated I 2 b) Islated CCl 2 6H 2 O 2 c) Islated CCl 2 d) Islated Sand e) Islated H 2 O f) Nne Circle the crrect chice [Slubility-density-vlatility-miscibility-nne] -Underline the crrect chice a) Islated I 2 b) Islated CCl 2 6H 2 O c) Islated CCl 2 d) Islated Sand e) Islated H 2 O f) Nne 3 *Circle the crrect chice [Slubility-density-vlatility-miscibility-nne] -Underline the crrect chice a) Islated I 2 b) Islated CCl 2 6H 2 O c) Islated CCl 2 d) Islated Sand e) Islated H 2 O f) Nne 4 *Circle the crrect chice [Slubility-density-vlatility-miscibility-nne] -Underline the crrect chice a) Islated I 2 b) Islated CCl 2 6H 2 O c) Islated CCl 2 d) Islated Sand e) Islated H 2 O f) Nne 5 Circle the crrect chice [Slubility-density-vlatility-miscibility-nne] -Underline the crrect chice a) Islated I 2 b) Islated CCl 2 6H 2 O c) Islated CCl 2 d) Islated Sand e) Islated H 2 O f) Nne 47

48 Flwchart Questins The flw chart has detailed steps labeled i x. Answer the fllwing questins cncerning prcedures labeled i x and supprt yur explanatin using yur experimental bservatins. Fr example yu may need t describe the clr f the gas generated in step 2, questin iii. If yu are naming a chemical, be sure yu spell-ut the crrect name and d nt abbreviate when referring t the chemical. i) What are the three substances that are mixed? ii) Which chemical is in the majrity in the mixture? iii) What is the clr f the gas? iv) What clr is the bttm f the dish? What is the identity f the chemical islated? v) What substance is added in rder t islate substance B frm C? vi) What is the clr f the aqueus slutin? vii) What techniques are used t islate the slid frm the liquid in this step? viii) What is the clr f the slid residue? What is the chemical identity f this residue? ix) What chemical is remved in rder t islate chemical C? x) What is the clr f the slid residue? What is the chemical identity f this residue? Additinal Questins 3. Describe ne separatin technique that yu learned abut in this experiment and hw it was used. 48

49 4. In this experiment, physical prperties were explited in the separatin f I2, sand and CCl2. In the separatin methds, physical changes were bserved with these substances. It is NOT pssible t separate cbalt frm chlride in CCl2 using physical changes. What kind f change wuld be required t separate cbalt frm chlride? 5. Hw des the additin f water change the physical prperties f the cbalt(ii) chlride substance? 49

50 Pst lab Questins Answer these pst lab questins and turn in t yur instructr befre yu leave lab. 1. What is the chemical identity f the purple gas when substance A, B and C are all heated? Justify yur answer by citing the evidence as written in yur bservatins in the datasheet. 2. Which ne f the three substances d we knw is nt sluble in water? Justify yur answer by citing the evidence as written in yur bservatins in the datasheet. 3. What is the chemical identity f the pwder blue slid in the last step? What clr des it change t when water is added? Yur answer must be unambiguus, s use detailed chemical frmulas, and the terms anhydrus and hydrate. Justify yur answer by citing the evidence as written in yur bservatins in the datasheet. 50

51 Exercise 8A: Balancing Chemical Equatins Last Name First Lab Partner(s): / pts Day aaaa. pppp. 1. Cmplete & balance the fllwing duble displacement reactin equatins: NaCl (aq) + AgNO3 (aq) NaOH (aq) + HCl (aq) BaCl2 (aq) + H2SO4 (aq) b. Cmplete, balance & Identify the type f reactin. Prduct names are named in parentheses (Cmbinatin, Decmpsitin, Single displacement, Duble displacement) Zn(s) + Cl2 (g) H2CO3(aq) (zinc chlride) (carbn dixide and water) Fe 2 S 3 (aq) + HCN (g) (Irn(III)cyanide and dihydrgen mnsulfide) Ni (s) + HCl (aq) (nickel(ii)chlride and hydrgen) BaO (aq) + CO2 (g) (barium carbnate) C(OH)3 (aq) + Na2CO3 (aq) (cbalt(iii) carbnate and sdium hydrxide) ZnCl2 (aq) + (NH4)2S (aq) (zinc sulfide and ammnium chlride) 51

52 c. Beneath each wrd equatin, write the frmula equatin and balance the reactin. Sulfur dixide (g) + Oxygen (g) Sulfur trixide (g) Ammnia (g) + xygen (g) water (g) + nitrgen mnxide (g) Ammnium nitrate (s) Nitrgen (g) + Oxygen (g) + Water (g) Sdium (s) + Acetic acid(aq) sdium (aq) + carbn dixide(g) + Water (g) bicarbnate acetate. Sdium bicarbnate (s) sdium carbnate (s) + carbn dixide (g) + Water (l) nitric acid (g) + nitrgen mnxide (g) nitrgen dixide (g) + Water (l) 52

53 Exercise 8B: Stichimetry Exercise Last Name First / pts Lab Partner(s): Day aaaa. 1. Mlar mass Find r calculate the atmic mass, mlar mass, r frmula mass fr the fllwing: (Include the apprpriate unit and rund ff t the hundredth f a unit.) a) Lead b) Phsphrus pppp. c) Sulfur hexafluride d) Sucrse (C12H22O11) 2. Atm, mlecules, mle, and Avgadr's Numbera) Hw many atms are in 11 mlecules f sulfur hexafluride? b) What is the mass in grams (g) f a single atm f Phsphrus? Hint: Start with the atmic mass r mlar mass f phsphrus and use dimensinal analysis t get grams per atm. c) What is the mass (in grams) f 5.0 mles f sucrse? 53

54 3. Balancing Equatins and the Mle Cncept a) Write and balance the chemical equatin and then determine the mles f ptassium chlrate (KClO3) prduced, if 17 mles f ptassium chlride is cmbined with excess xygen? b) Write and balance the chemical equatin and then determine the mles f H2O prduced frm cmbustin f 5 mles f sucrse and 39 mles f xygen? Which chemical is in excess and hw many mles remain after the reactin is cmplete? c) Hw many mles f S8 are needed t prduce 4.75 kg f sulfur tetrafluride accrding t the reactin: S 8 + F 2 sulfur tetrafluride. (Hint: First cmplete the equatin and balance if necessary) 54

55 d) What is the percent yield fr a reactin when grams f W2O3 cmbines with excess carbn mnxide t prduce g f W? W2O3 + CO W + CO2 e) Carbn dixide, CO2, and ammnia, NH3, cmbines tgether t frm urea, CH4N2O, plus water. Write a balanced equatin and calculate the mass f ammnia (in grams) that wuld be needed t make 2.0 mles f urea. 55

56

57 Experiment: Chemical Reactins & Chemical Equatins Objective In this experiment, students perfrm a variety f chemical reactins. Fr each reactin, student identify the signs that a reactin has ccurred, write the balanced chemical equatin with apprpriate phases and classify the reactin. Materials Cpper (BB bullets) Acetic acid (vinegar) Calcium xide (limewater) Small beaker Baking sda (NaHCO3) Spn Muriatic acid (HCl) Frceps Deinized water Ethanl Sugar (sucrse) Straw Magnesium Test tube Intrductin Reading: Chemistry in ur Lives Timberlake. Chapter 7.1 Equatins fr Chemical Reactins, 7.2 Types f Chemical Reactins, and 9.2 Electrlytes and Nn-Electrlytes. In this experiment, yu ll be bserving the signs f chemical reactins. These include the fllwing: Clr Change Frmatin f Bubbles, indicates that ne f the prducts is a gas. Ex. H2, O2 r H2O vapr Flame A change in temperature f the reactin mixture Frmatin f a precipitate. 57

58 Prcedure Reactin A: Oxidatin f Cpper by Air (O 2 ) Add cpper shts t a crucible s that it barely cvers the bttm. Psitin the pen crucible in a clay triangle supprted by an O-ring clamp attached t a ring stand. Heat the bttm f the crucible with a Bunsen burner until the bttm glws red. Turn ff the burner and allw the cntent t cl. Write n yur datasheet the balanced chemical equatin, the type f reactin and the driving frce fr the reactin. Empty all chemicals in the prper waste cntainer after yu finish. Reactin B: Cmbinatin f CaO with CO2 Pur limewater in t a 250 ml beaker. Using a straw, blw int the slutin. Observe what happens t the slutin as yu cntinue t blw bubbles. Write n yur datasheet the balanced chemical equatin, the type f reactin and the driving frce fr the reactin. Empty all chemicals in the prper waste cntainer after yu finish. Reactin C: Decmpsitin f H2O Using alligatr clips, cnnect the red wire t the psitive terminal f a 9-V battery and the black terminal t the negative terminal. Take care nt t tuch the bare ends f the terminal. Cnnect the ther ends f the alligatr clips t graphite rds. Take a glass f deinized water and add abut 1 gram f sdium chlride (abut a spatula tip). Place bth graphite rds int the water, taking care that they d nt tuch, and recrd yur bservatins. Write n yur datasheet the balanced chemical equatin, the type f reactin and the driving frce fr the reactin. When dne making yur bservatins, return all equipment clean and dry t its riginal strage lcatin. Reactin D: Cmbustin f Sucrse (C 12 H 22 O 11 ) Carry ut this prcedure under the hd. A deflagratin spn is used in this prcedure as shwn in the figure. Place a teaspn (~5 grams) f sugar in the deflagratin spn and then heat ver a Bunsen burner. Write n yur datasheet the balanced chemical equatin, the type f reactin and the driving frce fr the reactin. Empty all chemicals in the prper waste cntainer, clean the deflagratin spn and return t its riginal lcatin. Reactin E: Cmbustin f ethanl (C2H5OH) with xygen (O2). Carry ut this prcedure under the hd. A deflagratin spn is used in this prcedure as shwn in the figure belw. Add a small amunt f ethanl (~0.5 ml) t a deflagratin spn. Use a Bunsen burner t burn the ethanl. Only a small amunt f ethanl is necessary fr safety precautins. Write n yur datasheet the balanced chemical equatin, the type f reactin and the driving frce fr the reactin. Empty all chemicals in the prper waste cntainer when yu finish and return all equipment clean back t its riginal lcatin. Reactin F: Magnesium Ribbn with Muriatic Acid, HCl Add 2ml f Muriatic acid (HCl) t an empty test tube. Add a 1-cm strip magnesium ribbn t the test tube using a frceps. Write n yur datasheet the balanced chemical equatin, the type f reactin and the driving frce fr the reactin. Additinal Reactin: Fill a clean test tube with 2mL f deinized water. Place the test tube in a warm bath fr 5 min. Add tw drps f phenlphthalein indicatr t the water. Phenlphthalein is an indicatr that changes clr (pink) in the presence f hydrxides.* Add a 1-cm strip f magnesium t the test tube and wait 15 minutes fr the reactin t take place. After 15 minutes recrd in yur datasheet yur bservatin. Is there the presence f hydrxide frmatin? Write the chemical reactins that ccur in yur datasheet. * In general, alkalid metals will react with water t frm metal hydrxides and hydrgen gas. 58

59 Reactin G: Baking sda with Vinegar (CH3COOH). Halfway fill an evaprating dish with vinegar. Sprinkle baking sda n t the vinegar and recrd yur bservatins. Write n yur datasheet the balanced chemical equatin, the type f reactin and the driving frce fr the reactin. Empty all chemicals in the prper waste cntainer after yu finish. Hint: See Exercise 8A, if yu need help writing this equatin. Clean up Wash and dry all yur glassware equipment. Dispse f all used chemicals in the prper waste cntainer. Wipe dwn yur statin and place yur glassware and equipment back in its prper place. Unless yur equipment is back in the lcker drawer, yu are nt allwed t remve yur safety gggles. Wash yur hands thrughly with sap and water befre leaving yur wrk area. 59

60 60

61 Experiment 9: Data Sheets Last Name First / pts aaaa. Lab Partner(s): Day pppp. Reactin A: Oxidatin f Cpper by Air (O 2 ) t prduce cpper (II) xide Appearance Befre Appearance After Evidence f Reactin Balanced Chemical Equatin Reactin Type (circle ne) Cmbinatin - Decmpsitin - Single Displacement Cmbustin - Duble Displacement Reactin B: Cmbinatin f CaO with CO 2 t prduce calcium carbnate Appearance Befre Appearance After Evidence f Reactin Balanced Chemical Equatin Reactin Type (circle ne) Cmbinatin - Decmpsitin - Single Displacement Cmbustin - Duble Displacement 61

62 Reactin C: Decmpsitin f H2O int hydrgen and xygen gas Appearance Befre Appearance After Evidence f Reactin Balanced Chemical Equatin ** Reactin Type (circle ne) Cmbinatin - Decmpsitin - Single Displacement Cmbustin - Duble Displacement ** NaCl is used fr carrying f e- and is nt part f the chemical equatin. Reactin D: Cmbustin f Sucrse (C 12 H 22 O 11 ) Appearance Befre Appearance After Evidence f Reactin Balanced Chemical Equatin Reactin Type (circle ne) Cmbinatin - Decmpsitin - Single Displacement Cmbustin - Duble Displacement 62

63 Reactin E: Cmbustin f Ethanl (C2H5OH) with xygen (O2). Appearance Befre Appearance After Evidence f Reactin Balanced Chemical Equatin Reactin Type (circle ne) Cmbinatin - Decmpsitin - Single Displacement Cmbustin - Duble Displacement Reactin F: Magnesium Ribbn with Muriatic Acid, HCl t prduce hydrgen and magnesium chlride Appearance Befre Appearance After Evidence f Reactin Balanced Mlecular Chemical Equatin Ttal Inic Equatin Net Inic Equatin Reactin Type (circle ne) Cmbinatin - Decmpsitin - Single Displacement Cmbustin - Duble Displacement 63

64 Reactin G: Baking sda with Vinegar (CH3COOH). Appearance Befre Appearance After Evidence f Reactin Balanced Mlecular Chemical Equatin Ttal Inic Equatin Net Inic Equatin Reactin Type (circle ne) Cmbinatin - Decmpsitin - Single Displacement Cmbustin - Duble Displacement 64

65 Pstlab Questins 1. Check all the reactins in this lab, which prduced a precipitate. Oxidatin f Cpper Decmpsitin f H2O Reactin Mg ribbn with HCl Baking sda and Vinegar Cmbinatin f CaO and CO2 Decmpsitin f Sugar Ethanl with Oxygen 2. Check all reactins in this lab that shwed evidence f the release r absrptin f heat. (D nt cnfuse the release f heat with prviding an external additin f heat, ie. Heating with a Bunsen burner) Oxidatin f Cpper Decmpsitin f H2O Reactin Mg ribbn with HCl Baking sda and Vinegar Cmbinatin f CaO and CO2 Decmpsitin f Sugar Ethanl with Oxygen 3. Check all the reactins in this lab, which were accmpanied by the evlutin f gas. Oxidatin f Cpper Decmpsitin f H2O Reactin Mg ribbn with HCl Baking sda and Vinegar Cmbinatin f CaO and CO2 Decmpsitin f Sugar Ethanl with Oxygen 65

66 4. What is the clr f the sugar befre and after cmbustin? What is the identity f the gases yu bserved? 5. What is the gas frmed in the reactin between baking sda and vinegar? 66

67 Experiment: The Mle Last Name First Lab Partner(s): Day aaaa. Objective In this experiment, students use nuts (N) and blts (B) as mdel elements t build mdel cmpunds using these elements. Calculatins are perfrmed t identify unknwn cmpunds and t quantify a knwn cmpund. These calculatins mirrr the prcess fr using mlar mass t calculate the number f mles f a substance. This prcess is then applied t a mixture f lentil beans and t sme cmmn substances. The gal is t btain a deeper functinal understanding f the mle cncept and its use. Materials In Bin Bag f screws Bag f Lentils & Beans Bag f blts Unknwns in cnical vials In Rm Ally cube Sugar packet Distilled water Balance Intrductin Required additinal reading: Ch 7.4 the Mle and 7.5 Mlar Mass in Chemistry in ur Lives Timberlake 5 th Editin. pppp. 67

68 Prcedure Part I. Establishing the mass f individual elements and mlecules. These are fund in the clear cntainer. Open the cntainer t remve the 10 HexNuts and 10 Blts. A. Element #1 (the HexNut) and Element #2 (the Blt) Determine and recrd the fllwing infrmatin: i) The average mass f a single HexNut t the precisin f the scale. The best way t measure the average mass f a HexNut is t weigh 10 HexNuts and divide the ttal mass by 10. Shw yur wrk here. Ai) g ii) The average mass f a single Blt t the precisin f the scale. As mentined abve, the best way t measure the average mass f a blt is t weigh 10 blts and divide the ttal mass by 10. Shw yur wrk here. Aii) g Calculatins: B. Cmpunds #1 (BN), #2 (BN2), #3 (BN3) and #4(BN4): Blt HexNut mlecules The cmbined Blt (B) and HexNut (N) "elements" will represent ur theretical "cmpund" and will be represented by BN, BN 2, BN 3 and BN 4. Weigh the cntainer with the cmpund. Subtract the mass f the cntainer, calculate and recrd the average mass f the fllwing Blt-HexNut cmpunds. Shw yur calculatin f the average mass in the right-hand clumn. NAME Average Mass Calculatins BN Bi) g BN BN2 Bii) g BN2 BN3 Biii) BN3 BN4 Biv) BN4 68

69 C. The Lentil-Beans LB 5 These are fund in the plastic baggies labeled LB 5. D NOT pen this cntainer. i) Weigh the cntainer cntaining the 20 Lentil-Beans and recrd the grss mass in line Ci. Ci) g (grss) ii) Recrd the mass f the cntainer in line Cii. This mass is written n the label Cii) g Mass f cntainer iii) Subtract the mass f the cntainer frm the grss mass and write the net mass in line Ciii. Ciii) g 20 LB 5 (net) iv) Calculate the mass f ne-lentil-bean (LB 5 ) based n the data cllected. Civ) g Average Mass f LB 5 Calculatins: 69

70 Part 2. Cunting by Weighing. In this part f this lab, yu will determine the number f elements r cmpunds in a sealed cntainer by weighing the cntainer and its cntents and then using the infrmatin frm part I, yu will calculate the number f elements r mlecules. D. The number f HexNuts in a cntainer This unknwn is fund in the green cntainer. D NOT pen this cntainer. i) Recrd the mass f the unknwn HexNuts, (Element #1). ii) Recrd the mass f the cntainer as written n the label f the cntainer. iii) Calculate and recrd the net mass by subtracting the mass f the empty cntainer frm the grss mass measured. iv) Using the average mass f a single HexNut frm Part I, calculate the number f HexNut elements in yur unknwn. Shw yur calculatins belw. Yur answer must be a whle number. D i) g Mass f Cntainer+ HexNut (grss) D ii) g Mass f Cntainer (label n Cntainer) D iii) g Mass f HexNut in cntainer (net) D iv) number f HexNut in cntainer Calculatins fr D iv. E. The number f mlecules (BN) in a cntainer This unknwn ais fund in the range cntainer labeled Unknwn (BN). D NOT pen this cntainer. Lk fr the cntainer cntaining BN items. i) Recrd the mass f cntainer 2 in line Ei. This is the BN mlecules plus the cntainer. ii) Recrd the mass f the cntainer as written n the label f the cntainer in line Eii. iii) Calculate the net mass by subtracting the mass f the empty cntainer (as written n the cntainer) frm the grss mass measured. Write this mass in line E iii. iv) Using the average mass f a single BN cmpund, calculate the number f BN cmpund in yur unknwn and write this value in line E iv. Shw yur calculatins belw. Yur answer must be a whle number. E i) g Mass f cntainer + BN (grss) E ii) g Mass f cntainer (label n Cntainer) E iii) g Mass f BN in cntainer (net) E iv) number f BN cmpunds in cntainer Shw Calculatins n facing page. 70

71 F. The number f mlecules (Lentil-Bean, LB 5 ) in a cntainer This unknwn is fund in the purple cntainer labeled Unknwn (LB 5 ). D NOT pen this cntainer. i) Recrd the mass f cntainer #3 in line Fi. This is the Lentil-Bean mlecules plus the cntainer. ii) Recrd the mass f the cntainer as written n the label f the cntainer in line F ii. iii) Calculate and recrd net mass f the LB 5 in line F iii. F i) Mass f cntainer + LB5 (grss) F ii) Mass f cntainer (written n label) F iii) Mass f LB5 (net) iv) Using the average mass f a single LB 5 cmpund, calculate the number f LB 5 cmpund in yur unknwn and write this value in line F iv. Shw yur calculatins in the belw. Yur answer must be a whle number. F iv) number f Lentil-Bean in cntainer Calculatins fr F iv. Calculatins fr E iv. 71

72 Part 3. Identificatin f an Unknwn based n Average Mass. G & H: Determining the identity f the cmpund (BN, BN2, BN3 r BN4) These are fund in the Blue (G) and Yellw (H) cntainers labeled Unknwn (BN n ). D NOT pen these cntainers. Part G Part H i) Recrd the number f mlecules as written n the cntainers fr this part. Write these in line Gi and Hi. G i) # f mlecules H i) # f mlecules ii) Weigh each cntainer and recrd the mass in line Gii and Hii. G ii) g Mass f cntainer + Unknwn (grss) H ii) g Mass f cntainer + Unknwn (grss) iii) Recrd the mass f each cntainer as written n the label f the cntainers. Write the mass f each cntainer in lines Giii and Hiii. G iii) g Mass f cntainer H iii) g Mass cntainer iv) Calculate the net mass f the cntent in each cntainer. G iv) g Mass f Unknwn1 (net) H iv) g Mass f Unknwn2 (net) v) Take the net mass and divide by the ttal number f mlecules. This is the average mass f a single mlecule in the cntainer. Shw yur calculatins belw. vi) Using the data fr the average mass f the BN, BN 2, BN 3 and BN 4 frm part 1B, identify the chemical frmula f yur unknwn in the cntainer fr this part. Calculatins fr Gv and Hv. G v) g Average mass f Unk 1 G vi) Frmula f mlecule in cntainer H v) g Average mass f Unk 2 H vi) Frmula f mlecule in cntainer 72

73 Part 4. Calculatins, Cnverting frm Mass t Mles fr sme cmmn bjects. Using the mass f the irn cube, the 50.0mL f water and the packet f sugar, determine the number f mles f metal, water and sugar. Rund f t crrect number f significant figures and use scientific ntatin when apprpriate. I. The number f mles f Fe in a cube i) Metal cube: Weigh a metal cube and write the mass in line I i. I i) g Fe ii) Write the average atmic mass f Irn iii) Calculate the number f mles f the metal in the cube and write yur answer in line I ii. (Shw calculatins belw using dimensinal analysis) I ii) g/mle I iii) mles f irn iv) Hw many irn atms are in the cube? Calculatins fr Table I. I iv) atms f irn 73

74 J The number f mles f water in 50.0 ml f water i) 50.0 ml f water: Tare a 50mL-graduated cylinder n the scale. Add water and bring t precisely 50.0mL f water using a Berel pipet. Weigh the graduated cylinder with the water and recrd the mass. i) g 50.0 ml water ii) Add up the mlar mass f water and write yur answer t the right. ii) g/mle fr water iii) Calculate the number f mles f water in the 50- ml vlume f water. Shw yur calculatins belw. iii) mles f water Mve t Next Table answer questins belw as a Pst Lab iv) Calculate the number f water mlecules in 50.0 ml. Shw yur calculatins belw. iv) mlecules f water v) Calculate the number f Oxygen and H atms in 50 ml f water. Shw yur calculatins belw. Calculatins fr Table J v) O atms in water H atms in water 74

75 K. The number f mles f sucrse in a packet f sugar i) Packet f sucrse (sugar), C12H22O11: Weigh a packet f sugar and recrd the grss mass f the i) g mass f sugar + bag (grss) sugar packet. ii) Read and recrd the mass f the cntainer frm the label f the packet. ii) g mass f bag iii) Calculate the mass f the sugar in the packet and recrd in line Kiii. iii) g mass f sugar (net) iv) Calculate the mlar mass f sucrse (C12H22O11 ). Shw yur calculatins belw. iv) g/mle v) Calculate the number f mles f sucrse in the packet. Shw yur calculatins belw. v) mles f sugar Answer questins belw as a Pst Lab vi) Calculate the number f mlecules f sucrse in the packet f sugar. Shw yur calculatins belw. vi) mlecules f sugar vii) Calculate the number f atms f C, H, and O in the packet f sugar. Shw yur calculatins belw. Clean up - Replace all items in yur bin and bring back t the cart. Cmplete calculatins fr table K vii) C atms H atms O atms 75

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77 Experiment: Using Gas Laws t Identify an Unknwn Liquid Objective In this experiment, yu will use the Dumas methd t vaprize an unknwn vlatile liquid int the gas phase. While in the gas phase, the prperties f the gas will be measured, applied t a rearrangement f the Ideal Gas Law and used t calculate the mlar mass f the unknwn. The bjective is t identify the unknwn liquid based n its mlar mass frm a list f pssible liquids. Materials Unknwn Liquid Thermmeter 100-mL graduated cylinder 125-mL Ehrlenmeyer Flask 400 -ml Beaker Scale Ring stand Clamp Ht Plate Paper Clip Aluminum Fil Frceps r tngs Pipet Safety D nt inhale vaprs f the unknwn during the heating and evapratin steps f the prcedure. Intrductin In this experiment, yu will explit the prperties f matter in the gas phase t calculate the mlar mass (M) f an unknwn vlatile liquid. The liquid will be heated t evapratin inside a 125-L ehrlenmeyer flask s that it is entirely in the gas phase. An algebraic rearrangement f the Ideal Gas Law will be used t calculate the mlar mass. Relevant Equatins Ideal Gas Law : P = Pressure in units matching R V = Vlume f the gas in liters n = mles f gas T = temperature f the gas in Kelvin PPPP = nnnnnn 77

78 R = the ideal gas cnstant = l*atm/(ml K) = 62.4 l*mmhg/(ml K) The Ideal Gas Law can be rearranged t slve fr the number f mles f gas. nn = PPPP mm (gggggggggg) nn = RRRR MM ( gggggggggg mmmmmmmm ) Therefre, the equatin can be rearranged t calculate mlar mass (g/ml). MM = mmmmmm PPPP Similarly, this same equatin can be rearranged t slve fr the density f the gas. Recall the density f any frm f matter is the mass divided by the vlume (m/v). DD = mm VV = MMMM RRRR Cncepts behind the methd All calculatins using the Ideal Gas Law equatin, r its rearrangements, must usecnditins while the unknwn is in the vapr phase. There are sme assumptins that are made in the calculatins f the mlar mass (M) f the unknwn liquid. Pressure Initially, the unknwn is a liquid and exerts nly vapr pressure. The flask is filled with air. As the liquid bils, the air will be frced ut f the pinhle, and eventually there will n lnger be air remaining in the flask, and the nly gas will be the unknwn. The pressure f the vapr inside the flask is assumed t be the same as atmspheric pressure. T btain atmspheric pressure, use the barmeter in the frnt f the labratry rm, which reprts the pressure in units f mmhg. If there is n barmeter in the rm, yu may use the NOAA.gv website t get the lcal weather cnditins, which will be reprted in inches f mercury (inhg) and will need t be cnverted. Vlume The vlume f gas is defined by the cntainer in which it is cntained. In this experiment, this cntainer is the 125-ml ehrlenmeyer flask. The vlume f this flask will be accurately determined by measuring the mass f water cntained within it, and by transferring the water t a graduated cylinder and measuring. Temperature The temperature f the unknwn in the gas phase is assumed t be the same as the water bath, in which it is submerged. Fr this reasn, the temperature f the biling water is measured and applied t the gas law equatins. It is imprtant t have as much as the flask submerged as pssible withut spilling water int it. Mass f the Vapr It is nt pssible t put matter n a scale and measure its mass while it is in the vapr phase. Hwever, in this experiment, after the unknwn has cmpletely evaprated, the flask is ccupied cmpletely by the unknwn vapr. Once remved frm the heat and allwed t cl, the unknwn vapr will recndense and frm a liquid at the bttm f the flask. Yu may r may nt be able t see the liquid. Hwever, yu can determine the mass by recrding the mass f the flask, the fil and the cndensed liquid, and subtracting the mass f the flask and the fil that was recrded at the beginning f the experiment. Pssible Unknwns This table includes a list f pssible unknwns. Verify with yur instructr that this list is current as ptins may change frm semester t semester. Chemicals Frmula MM (g/ml) Acetnitrile Ethanl C2H3N C2H6O 78

79 Ethyl Acetate 2-Prpanl Isprpyl Acetate Hexane C4H8O2 C3H8O C5H10O2 C6H14 79

80 Prcedure Evapratin f the Vlatile Liquid, Mass f the vapr 1. Recrd in the datasheet the atmspheric pressure in the lab n the day f the experiment. Yur instructr will either prvide this infrmatin r shw yu hw t read the barmeter. 2. While the water is heating, btain 3 clean, dry 125-mL Erlenmeyer flasks and weigh it tgether with a square f aluminum fil. Recrd this cmbined mass in the datasheet (#1). 3. Als, remve the paper backing frm 3 squares f parafilm and weigh each flask with ne piece f parafilm (withut the fil). Recrd the mass in the datasheet rw #8. Set the parafilm aside. 4. Pur ~2-3 ml f yur assigned unknwn liquid int the flask. 5. Crimp the aluminum fil ver the muth f the flask t frm a cap; try t seal it as cmpletely as pssible. Fld the fil up s that it desn't hang dwn t far n the neck f the flask (~ 1 cm is far enugh). Using a pin, pke a small pinhle at the center tp f the fil. 6. Set up the apparatus fr the evapratin f yur unknwn liquid, as shwn t the right. Clamp the flask t the ring stand. If yu tilt the flask slightly, it may be easier t bserve when all the liquid has vaprized. Immerse the flask as much as pssible, s that the vapr inside the flask is unifrmly heated by the water. 7. Heat the water bath t biling and measure the temperature f the biling water. Be sure yu have at least reached the biling pint f water. Recrd this temperature in yur data sheet (#2). Cntinue heating until all the liquid inside the flask has vaprized, and heat fr at least 1 minute after all the liquid has vaprized. 8. Carefully remve the flask frm the ht water bath. Allw it t cl t rm temperature. Make sure it is cmpletely dry and carefully reweigh the flask with the fil. Recrd this mass in the datasheet (#6). Repeat this fr the secnd and third trial. Make sure that yu have weighed the ther flask befre yu begin the secnd and third trial. Determinatin f the Vlume f the Flask The vlume f the flask is the vlume f the vapr. After cmpleting the prcedure abve, yu will als determine the vlume f each flask used. This will be accmplished tw ways. First, the vlume will be calculated frm the mass f water held inside the Erlenmeyer flask using density. Vlume via mass f water 9. Discard the cndensed liquid frm yur last run and discard the aluminum fil, then rinse the flask 2-3 times with a small amunt f water. Fill the flask cmpletely water t the rim, seal the water in the flask with parafilm wax s the water desn t spill and then weight the water in the flask. Weigh the flask, parafilm and water and recrd in the datasheet in rw (#9) 10. Remve the parafilm and discard it, and measure the temperature f the water and recrd. 11. Using the mass f the flask/water/parafilm (#9) subtract the mass f the flask/parafilm t btain the mass f the water in the flask (#10). 12. Use the density f water at the temperature f the water t determine the vlume f the flask. 80

81 Vlume via vlume measurement f water A secnd methd t determine the vlume is t measure it directly using a graduated cylinder. 13. Begin with the flask filled cmpletely, all the way t the rim with water. There is mre than 100 ml f water in the erhlenmeyer flask, s yu will need t transfer the water t a 100-mL graduated cylinder in 2 stages. Recrd the vlume f water in the flask in rw #12 in the data sheets. Repeat this prcess tw mre times Clean up Wash and dry all yur glassware equipment. Dispse f all used chemicals in the prper waste cntainer. Wipe dwn yur statin and place yur glassware and equipment back in its prper place. Unless everyne s equipment is back in the lcker drawer, yu are nt allwed t remve yur safety gggles. Wash yur hands thrughly with sap and water befre leaving yur wrk area. 81

82 Experiment 11: Data Sheets Last Name First / pts Lab Partner(s): Day aaaa. Mass f the Vapr f an Unknwn Liquid Raw Data: Trial 1 Trial 2 Trial 3 pppp. 1. Mass f flask & Aluminum fil (g) 2. Temperature f vapr ( C) 3. Temperature f vapr (K) 4. Pressure f vapr (mm Hg) 5. Pressure f vapr (atm) 6. Mass f flask & fil & vapr (g) 7. Mass f vapr (g) Observatins. 82

83 Vlume f the Vapr Vlume f the flask via mass f the water Trial 1 Trial 2 Trial 3 8. Mass f flask & parafilm (g) 9. Mass f flask & parafilm & water (g) 14. Mass f water (g) 11. Density f water (g/ml) at temperature at 23 C g/ml g/ml g/ml 12. Use the density and mass f water t calculate the vlume f flask (ml) Vlume f the flask via the graduated cylinder Trial 1 Trial 2 Trial Vlume f flask via graduated cylinder (ml) Wrk Space fr calculatins. 83

84 Calculatin f Mlar mass and Density: 15. The Equatin fr mlar mass f a gas (M) 16. Mlar mass f vapr (g /ml) Shw sample calculatin here. MM = mmmmmm PPPP Trial 1 Trial 2 Trial Calculate the mean value f mlar mass f vapr fr the 3 trials. (g / ml) 18. The Equatin fr density f a gas 19. Take the Mlar Mass (M) and calculate the Density f the gas (g/l). Shw a sample calculatin here. DD = mm VV = MMMM RRRR 20. Mean value f density f vapr (g / L) Unknwn Number: Chemical name and frmula f unknwn: Mlar mass f unknwn: Use the frmula f the mlar mass f a gas and the density f a gas t fill the fllwing table. (Dn't frget t cnvert yur temperature t the abslute scale: T(K) = T( C) ; R = L atm/k ml) 84

85 Pstlab Questins Answer these pst lab questins and turn in t yur instructr befre yu leave lab unless tld therwise by instructr. 1. Tw methds were used t determine the vlume f the flask used fr the mlar mass determinatin. Which methd will give a mre precise determinatin f the vlume? Why? 2. It was imprtant that the flask be cmpletely dry befre the unknwn liquid was added s that water present wuld nt vaprize when the flask was heated. A typical single drp f liquid water has a vlume f apprximately ml. Assuming the density f liquid water is g/ml, hw many mles f water are in ne drp f liquid, and what vlume (ml) wuld this amunt f water ccupy when vaprized at 100. C and 1.0 atm? 85

86 86

87 Experiment: Cncentratin f a Salt Slutin Objective The purpse f this experiment is t determine the weight & cncentratin f disslved slids in salt-tainted water slutins. Cncentratin by parts (%, ppm & ppb) will be determined. Materials Salt-tainted water slutins Three beakers Ht plate Scale Graduated cylinder Heat gun 87

88 Intrductin Additinal Reading: Ch 9.4, Chemistry in ur Lives, 5 th Editin Timberlake. Slutin Cncentratins and Reactins. Fr this experiment, yu will be determining the cncentratin f a saline slutin f unknwn cncentratin. Yur results will be reprted in a mass percent (m/m %), ppm and ppb. A prtin f yur grade will reflect the accuracy and precisin f yur results. 88

89 Prcedure 1. Yur instructr will assign yu an unknwn. This unknwn is the salt-tainted water sample and be sure t d three trials then average the results. Use the three largest beakers in yur lab drawer fr this prcedure. The large beakers prvide wider surface area, which allws fr faster evapratin f the water during the experiment. Thrughly clean with sap and water three beaker and be sure it is dry. Inspect the glassware fr stress, stars r cracks, if yu suspect yur beaker will break, have yur instructr inspect yur beaker and change it ut if necessary. 2. Label the beakers with "1", "2" and 3 n the side. Weigh each f the beakers n the balance t the thusandth f a gram (0.001 g). Write the mass f each beaker in yur reprt sheet. 3. Measure ~100 ml f the salt-tainted water sample that has been assigned t using a 100mL beaker and pur it int beaker labeled 1. D nt wrry abut reading the exact vlume since the amunt f water will be weighed. Repeat this fr trials 2 and 3. Weigh each beaker, which cntains the salt-tainted water slutin n the balance t the nearest thusandth f a gram (0.001 g). Write this weight as the " Mass Salt-tainted slutin + beaker" measurement. Repeat this fr the ther tw samples. 4. Place each beaker n the ht plate and heat the beaker s that the water bils gently. The rate f biling can be cntrlled by adjusting the heating dial r by mving the beaker away frm the center tward the side f the htplate. When the vlume f water sample has finally biled dwn t abut 5-10 ml, it is advisable t cver the beaker with a watch glass t catch spattering frm the cncentrated slutin. When the beaker is dry, rinse the splattering ff the watch glass back int the beaker with a little deinized water using a water bttle. Because the watch glass is ht, it is necessary t hld it with tngs. Evaprate the small amunt f water in the beaker t dryness by heating the dish gently withut the watch glass. 5. When the slutin is dwn t abut 0.5 ml, remve reduce the heat by mving the beaker t the side f the ht plate and reduce the temperature setting. When all the water in the beaker has evaprated, carefully use mitts t remve the beaker and place it n the wire screen n the lab bench. If there is still water alng the walls f the beaker, use the heat gun t evaprate the residual misture. * Frm this pint n, use tngs r ht mitts t handle the beaker s that il frm yur fingers d nt add t the mass f the residue. Use the ven-mitts t handle the ht beaker and d nt tuch the ht beaker directly. 6. Nte and recrd the clr f the residue (residual salt) and describe in yur data sheet. 7. Allw the beaker t cl fr an additinal minutes making sure that there is n residual water remaining. 8. Weigh each beaker which cntains the residue and write the result in yur datasheet as " Mass beaker + residue ". Use the weight f "beaker", the weight f "beakers + water" and the weight f "beaker + residue" t calculate the weight f disslved slids in the water sample and the amunt f ttal disslved slids (TDS) in yur sample. Express the TDS in parts per hundred (% mass), parts per millin (ppm) and parts per billin (ppb). Be sure t use the crrect number f significant figures in yur calculatins. Clean up Wash and dry all yur glassware equipment. Dispse f all used chemicals in the prper waste cntainer. Wipe dwn yur statin and place yur glassware and equipment back in its prper place. Unless yur equipment is back in the lcker drawer, yu are nt allwed t remve yur safety gggles. Wash yur hands thrughly with sap and water befre leaving yur wrk area. 89

90 Experiment 12: Data Sheets Last Name First / pts aaaa. Lab Partner(s): Day pppp. A. Datasheet Unknwn # Sample 1 Sample 2 Sample 3 Descriptin f sample: 1. Apprximate vlume f salttainted slutin, measured frm graduated cylinder: 2. Mass f beaker: 3. Mass f slutin + beaker: 4. Mass beaker + residue (salt): 5. Mass f residue 6. Mass f slutin: Shw ne sample calculatin in prper frmat fr Mass f residue and mass f slutin: 90

91 B. % (m/m) f Salt Slutin 7. % cncentratin (m:m) 8. Average % Cncentratin Shw ne sample calculatin in prper frmat fr the % cncentratin f yur slutin and the calculatin f the average. C. Parts per millin (ppm) and Parts per billin (ppb) 9. ppm 10. Average ppm 11. ppb 12. Average ppb Shw ne sample calculatin in prper frmat fr the ppm and ppb yur slutin. 91

92 Pstlab Questins 1. If the residue is nt heated t dryness but is still smewhat mist, hw wuld this change the final amunt f residue calculated in the slutin? Wuld yu expect the calculated cncentratin f the residue t be higher r lwer than the true value? (Check mark and prvide explanatin) Cncentratin: Higher Lwer N Change Nt enugh infrmatin than true value. 2. If a large piece f dirt, say 10 mg, falls int the beaker just after the sample is evaprated t dryness and is weighed, what effect wuld this have n the weight f disslved slids fund? Wuld yu expect the calculated cncentratin f the residue t be higher r lwer than the true value? (Check mark and prvide explanatin) Cncentratin: Higher Lwer N Change Nt enugh infrmatin than true value. 3. If a large amunt f water splatters ut f the beaker, say ~10 ml, during the evapratin prcess. Explain hw wuld this affect the mass f the residue calculated in yur result? Wuld yu expect the calculated cncentratin f the residue t be higher r lwer than the true value? Cncentratin: Higher Lwer N Change Nt enugh infrmatin than true value. 4. If yu calculated a salt-tainted slutin f abut 3.5% *, what wuld the mlarity f this slutin? Assume the density f this slutin is 1.03 g/ml. (* BTW, this is the salinity f seawater) 92

93 Experiment: Intrductin t Equilibrium and LeChatelier s Principle Objective The bjective f this experiment is t determine the effects f disturbances n chemical systems at equilibrium. The respnse f the chemical systems will be justified in terms t LeChatelier's principle. Materials Brmthyml Blue 0.1 M Zn(NO3)2 NH4Cl saturated slutin Phenlphthalein 15 ml Club Sda NH4Cl crystals 0.1 M NaOH 6 M NaOH Distilled water 0.1M HCl 6 M HCl Test tubes Syringe with cap Safety Nte: 6M HCl and 6M NaOH are strng acid and a strng base and shuld be handled with care. 0.1 M Hydrchlric (HCl) acid-crrsive and 0.1 M sdium hydrxide-txic, crrsive, and irritant. Prevent cntact with yur eyes, skin, and clthing. Avid ingesting the substance. If yu spill any slutin, immediately ntify yur labratry instructr. Intrductin Required additinal reading: Fr a mre cmplete descriptin f Equilibrium and LeChatelier s Principle, read Chemistry in ur Lives, 5 th Editin Timberlake. Ch10.2 Chemical Equilibrium and 10.5 Changing Equilibrium Cnditins: Le Chatelier s Principle. Fr this experiment, yu will be establishing chemical equilibria and bserving the effects f perturbatins n the equilibria. Yu will be asked t explain yur bservatins in terms f the chemical equilibrium reactin equatin and Le Chatelier s Principle. Le Chatelier s Principle states that when a system at equilibrium is expsed t a stress, the system will shift t re-establish equilibrium. There are many kinds f stresses t systems at equilibrium. Effects f Changing Cncentratin f Reactants r Prducts Changing the cncentratins f reactants r prducts f a system at equilibrium will cause the system t respnd t reestablish the equilibrium cnditins. aa + bb cc + dd Cnsider the abve reactin with reactants, A and B, and prducts, C and D, and the related equilibrium expressin. KK eeee = [CC]cc [DD] dd [AA] aa [BB] bb Keq is a cnstant, s a change in the cncentratins f ne r mre f A, B, C r D, must result in a change in the ther species invlved in the equilibrium t keep the right side f the equatin equal t Keq. Excess Stress: Effect f Increasing Cncentratins An increase in the cncentratin f reactant A t the abve system at equilibrium will cause an excess stress. The system will reestablish equilibrium by cnsuming A and shifting the reactant tward prducts. An increase in prduct C r D will shift the equilibrium t the left. 93

94 Deficit Stress: Effect f Decreasing Cncentratins Anther means f disturbing a chemical system at equilibrium is t reduce the amunt f ne f the cmpnents, a deficit stress. Fr instance, we culd reduce the amunt f prduct C in the system at equilibrium. The system wuld respnd by shifting t the right t replenish C and establish a new equilibrium state. This phenmenn can be used t increase the yield f a prduct at equilibrium. One way t affect a deficit stress is t remve a prduct r reactant with a secndary r side reactin that cnsumes the chemical species. In ur abve system, it wuld be represented as illustrated belw. A + B + X C + D AX X reacts with A t create the prduct AX. If X is added t this system at equilibrium, it will cause a deficit stress fr reactant A. Thus the equilibrium will shift tward reactants t replenish reactant A. In the reactin fr the Haber prcess shwn belw, remving the NH 3 as it frms during the reactin can increase the yield f NH3, when the equilibrium shifts t replace it. N2 (g) + 3 H2 (g) 2 NH3(g) Fr this experiment, yu will need t identify deficit stresses created this way. It will be useful t knw the fllwing reactin. H + (aq) + OH - (aq) H2O (l) The Effect f Pressure LeChatelier s Principle states that fr equilibria cntaining gases, an increase in pressure, will disturb the system, and shift the reactin t the side with the lesser number f mles f gas. A decrease in the mles f gas will reduce the pressure in the reactin vessel. If the vlume f the vessel is increased, the crrespnding decrease in pressure will cause a shift in the equilibrium tward the side that has mre gas mlecules. If a reactin is such that there are equal number f mles f gas in the reactant and the prduct, then there is n effect n the equilibrium as a result f a vlume change in the reactin vessel. The Effect f Temperature A change in temperature will als stress an equilibrium. An exthermic reactin is ne that releases heat, that is, the energy f the reactants is greater than that f the prducts. Since heat is released as the reactin prgress in the frward directin then heat can be cnsidered a prduct. A temperature increase fr an exthermic reactin will cause the equilibrium t shift t the t alleviate the excess heat stress caused n the right (prduct) side f the reactin. Fr example, the Haber prcess is exthermic, and can be written: N 2 (g) + 3H 2 (g) 2NH 3(g) + heat Heat is released as a prduct f the frward reactin. A temperature increase causes the equilibrium t shift t the left, resulting in a reduced amunt f heat and NH 3, and an increase prductin f N 2 and H 2. Slubility f gases is anther example f exthermic prcesses. An endthermic reactin is ne that absrbs heat. The energy f the prducts is greater than that f the reactants. Since heat is required fr the frward reactin t ccur. In this case heat is treated as a reactant in the chemical equatin. Therefre, a temperature increase will cause the equilibrium t shift t the right. Table 1 summarizes the stresses and respnses t perturbatins f a system at equilibrium. In this labratry experiment, yu will need t identify the type f stress that yu have affected fr several equilibrium reactins 94

95 and the respnse. Yur answers shuld cite a stress frm this table. Yur descriptin must include the specific details, reactants r prducts, f the reactin yu are studying. A clear descriptin f the details as they relate t Table 1, will demnstrate t yur instructr that yu have a clear understanding f the cncepts related t LeChatelier s Principle. Table 1 Summary f Equilibrium Stresses and Respnse Stress Respnse Shift Increase [reactants] Cnsume the reactants Increase [prducts] Cnsume the prducts Decrease [reactants] Replenish the reactants Decrease [prducts] Prduce mre prducts Increase Pressure Shift t reduce pressure Shift t side with fewer mles f gas Decrease Pressure Shift t increase pressure Shift t side with mre mles f gas Increase Temperature -Endthermic Reactin Cnsume the heat - Exthermic Reactin Cnsume the heat Decrease Temperature Endthermic Reactin Prduce heat -Exthermic Reactin Prduce heat The Observables in this Experiment Many chemical reactins ccur withut a directly bservable change in the reactin vessel. Fr this experiment, reactins in equilibrium have been selected that have bservable physical prperties in the reactants, prducts r bth. Table 2 Reactin Reactants Prducts (Eq. 1) HInd (aq, yellw) H+(aq) + Ind-(aq, blue) Yellw Blue (Eq. 2) Zn 2+ (aq) + 2OH - (aq) Zn(OH)2 (s) Clear, clrless Turbid, White i i (Eq. 3) H2CO3(aq) H2O(l) + CO2 (g) Clear, Clrless Bubbles (Eq. 4) NH4Cl(s) NH4 + (aq) + Cl - (aq) Turbid, White i i Clear, Clrless 95

96 Prcedure Prepare a ht water bath befre starting these prcedures. A. Brmthyml Blue in equilibrium between yellw (Hind) and blue (Ind-) frms: (Eq. 1) HInd (aq, yellw) H+(aq) + Ind-(aq, blue) Cautin: 0.1 M Hydrchlric (HCl) acid-crrsive and 0.1 M sdium hydrxide-txic, crrsive, and irritant. Prevent cntact with yur eyes, skin, and clthing. Avid ingesting the substance. If yu spill any slutin, immediately ntify yur labratry instructr. 1. Half-fill a clean, dry test tube with deinized water. Add 2 drps f the indicatr, brmthyml blue. Recrd the clr f the slutin n yur datasheet (1). 2. Add 0.1 M NaOH, drpwise, while stirring with a clean, dry, glass, stirring rd until a clr change ccurs. Add 2 mre drps. Recrd yur bservatins n yur datasheet (2). 3. Add 0.1 M HCl, drpwise, while stirring with a clean, dry, glass, stirring rd until a clr change ccurs. Recrd yur bservatins n yur datasheet (3). 4. Again, add 0.1 M NaOH, drpwise, while stirring with a clean, dry, glass stirring rd until a clr change ccurs. Recrd yur bservatins n yur datasheet (4). 5. Experiment by adding the right amunt f acid (HCl) drpwise t this test tube t make the slutin turn greenish in clr after it is stirred. Recrd yur bservatins n yur datasheet (5). Include hw many drps were needed. 6. Pur all waste in the labeled waste cntainer at the apprpriate statin. Rinse the test tube with 3-5 ml f tap water and empty the rinse in the waste cntainer. Finally, rinse the test tube with deinized water. B. Slubility f Zinc Hydrxide : (Eq.2) Zn 2+ (aq) + 2OH - (aq) Zn(OH)2 (s) Cautin: Cncentrated NaOH is txic, crrsive, an irritant and can cause burns. Prevent cntact with yur eyes, skin, and clthing. Avid ingesting the substance. If yu spill any slutin, immediately ntify yur labratry instructr. 1. Using a Beral pipet, add 20 drps (~1 ml) f 0.1M Zn(NO3)2 t a clean, dry test tube. Add 1 drp f 6M NaOH. Stir with a clean, dry, glass stirring rd. Recrd yur bservatins n yur datasheet (2 a). 2. Add 6M HCl, drpwise, while stirring with a clean, dry, glass, stirring rd until a clr change ccurs and n mre changes are seen. Recrd yur bservatins n yur datasheet (2 b). 3. Using a Beral pipet, add 20 drps (~1 ml) f 0.1M Zn(NO3)2 t a secnd clean, dry test tube. Add 1 drp f 6M NaOH. Stir with a clean, dry, glass stirring rd. 4. Add 6M NaOH, drpwise, while stirring with a clean, dry, glass, stirring rd until a clr change ccurs and n mre changes are seen. Recrd yur bservatins n yur datasheet (2 d). 5. Pur all waste in the labeled waste cntainer at the apprpriate statin. Rinse the test tubes with 3-5 ml f tap water and empty the rinse in the waste cntainer. Finally, rinse the test tubes with deinized water. C. Carbnic acid and Carbn Dixide (Eq. 3) H2CO3(aq) H2O(l) + CO2 (g) 1. Remve plunger frm syringe and place cap n the end. T the syringe, add apprximately 15 ml f club sda. Reinsert plunger, invert syringe s that it is pinting up, remve cap and push n plunger s there is 96

97 n gap between the plunger and the sda. Replace cap. Yu shuld see bubbles in the sda slutin, if yu dn t pull the plunger slightly until sme bubbles frm. 2. Observe the bubbles within the syringe and recrd bservatins n yur datasheet (1). 3. Increase the pressure by squeezing dwn n the plunger. Keep the syringe tip pressed n the bench tp s that the syringe cap des nt get pushed ff. Observe any changes in the bubbles. Recrd bservatins n yur datasheet (2). 4. Increase the vlume in the syringe and therefre decreasing the pressure in syringe by slwly pulling ut the plunger but d NOT cmpletely remve the plunger frm the syringe. Observe any changes in the bubbles. Recrd bservatins n yur datasheet (3). 5. Carry ut a prcedure t determine the thermicity (endthermic r exthermic) f equatin 3. T d this start with a syringe that shws bubbles in the sda then place either in ht r cld water. Circle the crrect chice fr this reactin, endthermic r exthermic. (4) 6. Empty syringe cntents int the sink. Thrughly rinse syringe with tap water, fllwed by deinized water. D. Slubility f Ammnium Chlride (Eq. 4) NH4Cl(s) NH4 + (aq) + Cl - (aq) Cautin: Cncentrated HCl is txic, crrsive, and can cause burns. Prevent cntact with yur eyes, skin, and clthing. Avid ingesting the substance. If yu spill any slutin, immediately ntify yur labratry instructr. 1. Measure 3 ml f saturated NH4Cl slutin in a clean test tube. Add 1 drp f cncentrated HCl, while stirring the test tube. Cntinue adding cncentrated HCl drpwise, stirring after each additin, until a change ccurs. Recrd yur bservatins n yur datasheet (1). 2. Using a test tube hlder, place the test tube int the biling water in the ht-water bath. Stir the slutin in the test tube while heating fr 3 min. Recrd yur bservatins n yur datasheet (2). 3. Add ice t a 400mL beaker t the half way mark and then fill with water up t the 300mL level. Using a test tube hlder remve yur test tube frm the biling water and place it in the cld-water bath. Leave the test tube in the cld-water bath fr 3-5 minutes. Recrd yur bservatins f yur datasheet (3). 4. Using a test tube hlder remve the test tube frm the cld-water bath and place back in the ht water bath. Recrd yur bservatins n yur datasheet (4) 5. Turn ff the ht plate and allw the ht plate t cl befre returning it back t its strage space. 6. Pur all waste in the labeled waste cntainer at the apprpriate statin. Rinse the graduated cylinder and the test tube with 3-5 ml f tap water each and then empty the rinse in the waste cntainer. 7. Using a clean spatula, add enugh crystals f slid NH4Cl t cver the bttm f a secnd clean, dry test tube. 8. Add 5 ml f deinized water nt the slid NH4Cl in the test tube. Stir the mixture. Feel the test tube t determine if the disslutin f NH4Cl prduces a temperature change. Recrd yur bservatins (5). 9. Pur all waste in the labeled waste cntainer at the apprpriate statin. Rinse the graduated cylinder and the test tube with 3-5 ml f tap water each and then empty the rinse in the waste cntainer. Wash all yur glassware and dispse f all used chemicals in the prper waste cntainers. Clean up Wash and dry all yur glassware equipment. Dispse f all used chemicals in the prper waste cntainer. Wipe dwn yur statin and place yur glassware and equipment back in its prper place. Unless yur equipment is back in the lcker drawer, yu are nt allwed t remve yur safety gggles. Wash yur hands thrughly with sap and water befre leaving yur wrk area. 97

98 98

99 Experiment 13: Data Sheets Last Name First / pts Lab Partner(s): Day aaaa. A. Brmthyml Blue in equilibrium: HInd (aq, yellw) H+(aq) + Ind-(aq, blue) 1. Check mark the clr f the slutin after additin f indicatr brmthyml blue. pppp. Yellw Blue Clrless Green Orange White 2. Check mark the change that yu bserve after additin f NaOH. Turns Yellw Turns Blue Turns Clrless Turns Green Turns Orange Turns White If nne f the chices match, write yur wn descriptin here. 3. Check mark the change that yu bserve after additin f HCl. Turns Yellw Turns Blue Turns Clrless Turns Green Turns Orange Turns White If nne f the chices match, write yur wn descriptin here. 4. Check mark the change that yu bserve after re-additin f NaOH. Turns Yellw Turns Blue Turns Clrless Turns Green Turns Orange Turns White If nne f the chices match, write yur wn descriptin here. 5. Hw many drps were f HCl were needed t btain a greenish clr? 6. Using LeChatelier's Principle and citingtable 13.1 and the clr changes yu bserved, a) Briefly explain hw the additin f NaOH affects the equilibrium. b) Briefly explain hw the additin f HCl affects the equilibrium. 99

100 100

101 B. Slubility f Zinc Hydrxide : Zn 2+ (aq) + 2OH - (aq) Zn(OH)2 (s) 1. Check mark the clr f the slutin after additin f 1 drp NaOH. Yellw slutin Blue slutin Clrless slutin range slutin Pink slutin White precipitate 2. Check mark the change that yu bserve after additin f HCl. slutin turns yellw slutin turns blue slutin turns clrless slutin turns green slutin turns range white precipitate frms If nne f the chices match, write yur wn descriptin here. 3. Check mark the change that yu bserve after additin f Zn(NO3)2. slutin turns yellw slutin turns blue slutin turns clrless slutin turns green slutin turns range white precipitate frms If nne f the chices match, write yur wn descriptin here. 4. (2 d) Check mark the change that yu bserve after drpwise additin f NaOH. slutin turns yellw slutin turns blue slutin turns clrless slutin turns green slutin turns range white precipitate frms If nne f the chices match, write yur wn descriptin here. 4. Using Le Chatelier's Principle and Table 13.1 explain the changes yu bserved, a) Briefly explain hw the additin f HCl affects the equilibrium. b) Briefly explain hw the additin f a small amunt f NaOH affects the equilibrium. c) Briefly explain hw the additin f a larger amunt f NaOH affects the equilibrium. 101

102 C. Carbnic acid and Carbn Dixide (Eq. 3) H2CO3(aq) H2O(l) + CO2 (g) 1. Check mark all that applies fr yur bservatins f the fate f the bubbles in this part f the experiment. There are n bubbles Mre bubbles frm Less bubbles frm Bubbles becme smaller Bubbles becme bigger Bubbles des nt change If nne f the chices match, write yur wn descriptin here. 2. Check mark all that applies fr yur bservatins f the fate f the bubbles in this part f the experiment. There are n bubbles Mre bubbles frm Less bubbles frm Bubbles becme smaller Bubbles becme bigger Bubbles des nt change If nne f the chices match, write yur wn descriptin here. 3. Check mark all that applies fr yur bservatins f the fate f the bubbles in this part f the experiment. There are n bubbles Mre bubbles frm Less bubbles frm Bubbles becme smaller Bubbles becme bigger Bubbles des nt change If nne f the chices match, write yur wn descriptin here. 4. What is the thermicity f this equilibrium? Endthermic Exthermic Supprt yur chice by describing yur bservatins. 5. Using LeChatelier's Principle and citing Table 13.1 explain the changes yu bserved, a) Briefly explain hw the pushing n the plunger affects the equilibrium. b) Briefly explain hw pulling back n the plunger affects the equilibrium. 102

103 D. Slubility f Ammnium Chlride (Eq. 4) NH4Cl(s) NH4 + (aq) + Cl - (aq) 1. Check mark all the chices belw that is cnsistent f what yu bserved after additin f HCl. The slutin starts clear The slutin starts white The slutin starts with different clr The slutin turns clear The slutin turns white The slutin stays the same 2. Check mark all the chices belw that are cnsistent f what yu bserved after heating the test tube. The slutin starts clear The slutin starts white The slutin starts with different clr The slutin turns clear The slutin turns white The slutin stays the same If nne f the chices match, write yur wn descriptin here. 3. Check mark all the chices belw that is cnsistent f what yu bserved after cling the test tube. The slutin starts clear The slutin starts white The slutin starts with different clr The slutin turns clear The slutin turns white The slutin stays the same If nne f the chices match, write yur wn descriptin here. 4. Check mark all the chices belw that is cnsistent f what yu bserved after reheating the test tube. The slutin starts clear The slutin starts white The slutin starts with different clr The slutin turns clear The slutin turns white The slutin stays the same If nne f the chices match, write yur wn descriptin here. 5. Check mark all the chices belw that is cnsistent f what yu bserved after disslving the NH4Cl in deinized water. The slutin starts clear The slutin starts white The slutin starts with different clr The slutin turns clear The slutin turns white The slutin stays the same If nne f the chices match, write yur wn descriptin here. 6. Was there a temperature change in this prcedure? Slutin warmed up Slutin cled dwn N temperature change 7. Is the disslutin (disslving) f NH4Cl exthermic r endthermic? Endthermic Exthermic 8. Rewrite the net equatin fr the disslutin f NH4Cl, including heat as either a reactant r prduct. 9) Using LeChatelier's Principle and citing Table 13.1 explain the changes yu bserved, a) briefly explain hw the additin f HCl affects the equilibrium. b) briefly explain hw the change in temperature affects the equilibrium. 103

104 dpst-labratry Questins 1. The ppular antacid, Milk f Magnesia, is a suspensin f magnesium hydrxide, Mg(OH)2. In water, Mg(OH)2 underges the reactin shwn : Mg(OH)2 (S, white) Mg 2+ (aq) + 2 OH - (aq) a) If an acid (H+) were added t this mixture, which species wuld it react with? b) Wuld this cause an excess r deficit stress n that species? c) Predict if the slutin will appear mre cludy r mre clear after the additin f acid. d) Use LeChatelier's Principle t explain yur predicted bservatin in (c). 2. Cnsider the gas equilibrium that yu studied in this experiment. If we are tld that the equilibrium favrs the right side f the equatin, is the value f Keq a relatively large number r a relatively small number? Briefly explain using yur knwledge f determining Keq. 3. In Step 1 E, after btaining a greenish clr, what des this tell yu abut the relative cncentratins f HInd and Ind- in the slutin? 104

105 Experiment: Titratin f Vinegar Objective The purpse f this experiment is t determine the mlarity and weight/vlume percent cncentratin f acetic acid in husehld vinegar by titratin with sdium hydrxide t a phenlphthalein endpint. Materials Deinized water vinegar M NaOH Phenlphthalein 250-ml beaker 50-ml buret 250-ml Erlenmeyer flask 400-ml beaker fr waste White paper (2-3 sheets) 5-ml vlumetric pipette Intrductin Required additinal reading: Fr a mre cmplete descriptin f Titratins, read Chemistry in ur Lives, 5 th Editin Timberlake. Ch11.8 Acid-Base Titratin. Prcedure Table A. Setup 1. Recrd the brand f vinegar and its weight / vlume percent f acetic acid in yur wrksheet. 2. Using a 5 ml vlumetric pipette, place 5.00 ml f vinegar in a clean 250 ml Erlenmeyer flask (r a 125mL Erlenmeyer flask). The flask des nt need t be dry but it must be clean and rinsed with deinized water. Recrd the vlume f vinegar in yur ntebk. 3. T the Erlenmeyer flask cntaining the vinegar, add apprximately 25 ml f deinized water and swirl gently t mix. Use hydr-in paper t measure the ph at this pint, and recrd in Table A. NOTE: Take care t avid spattering f the vinegar nt the sides f the flask when yu are swirling the slutin. The additin f water will nt change yur final results. This is simply t increase the accuracy f the titratin. 4. T the same flask, carefully add 3-4 drps f the phenlphthalein indicatr using the drpper prvided. NOTE: D nt add mre than 4 drps f indicatr. This is the critical step in the titratin. If yu fail t add indicatr, then yu will never see a clr change in yur slutin. 5. Set up a titratin apparatus as shwn t the right and place a piece f white paper underneath the flask. NOTE: This white paper will make the clr change frm clear t pink easier t see. 6. Using a 150 ml beaker, btain apprximately 75ml f M NaOH slutin The exact cncentratin f the NaOH will be labeled in the cntainer. Recrd the mlarity f the NaOH slutin in Table A. CAUTION: If yu spill NaOH slutin at any step in this experiment, call yur instructr immediately. 7. Making sure that the stpcck f the buret is in the clsed psitin, rinse yur buret with 10 ml f the NaOH slutin. NOTE: Yur instructr will demnstrate this technique. 105

106 Table B. Titratin 8. Using a funnel, slwly fill the buret t slightly abve the 0.00 ml mark with the NaOH slutin. Carefully pen the stpcck and slwly drain the NaOH slutin int a waste beaker until the meniscus f the slutin is belw the 0.00 ml mark. NOTE: If yu have air bubbles in the tip f the buret after this step, call yur instructr. 9. Recrd in yur ntebk the initial level f the NaOH slutin in the buret t the hundredth f a ml. 10. Begin adding the NaOH slutin t the vinegar slutin prepared in Steps 2-4. T d this, add the NaOH in small amunts (abut 1 ml/min) while cntinuusly swirling the flask in a gentle, circular mtin. Make sure that the tip f the buret extends slightly int the muth f the flask, and take care t avid spattering f the slutins nt the sides f the flask. Recrd the final level f NaOH in the buret after the endpint has been reached. NOTE: While adding the NaOH slutin, yu will see the frmatin f temprary pink "cluds" in the vinegar slutin. As this pink clratin begins t take lnger and lnger t disappear, slw the rate f additin f the NaOH slutin t abut 10 drps/minute. The endpint f the titratin is reached when ne drp f the NaOH slutin changes the vinegar slutin frm clrless t a pale, pale pink that permanently remains even after swirling the slutin. 11. In yur ntebk, recrd the vlume f NaOH slutin delivered frm the buret during the titratin. This vlume is the difference between the final buret reading (at the endpint) and the initial buret reading. 12. Use a hydr-in paper t measure the ph at this pint. 13. Repeat steps 1-12 until yu have three titratins that agree with 0.50 ml. Clean up Wash and dry all yur glassware equipment. Dispse f all used chemicals in the prper waste cntainer. Wipe dwn yur statin and place yur glassware and equipment back in its prper place. Wash yur hands thrughly with sap and water befre leaving yur wrk area. 106

107 Table C. Calculatins f the Mlarity f the Acid Shw yur calculatins fr each Rw f Table C in the space prvided in the center clumn. 14. Calculate average vlume f NaOH used in the titratin fr the 3 trials and recrd the vlume in ml in the tp rw f Table C. Shw yur calculatins 15. Cnvert the average vlume frm ml t L and recrd in Table C. 16. Use the cncentratin f the NaOH t calculate the average number f mles f NaOH used in the titratins and recrd in Table C. 17. The number f mles f acid is equal t the number f mles f base at the endpint f a titratin. Yur answer fr the number f mles f acid will be the same as the number f mles f base used. 18. T calculate the mlarity (mles/liter) f the vinegar, divide the mles f acid by the vlume (in liters) f vinegar that was titrated. 107

108 108

109 Experiment 14: Data Sheets Last Name First Day / pts Lab Partner(s): Table A: Setup Infrmatin Brand f Vinegar Weight/Vlume % (Frm Label) Vlume f Vinegar Mlarity f NaOH ph f Vinegar Table B: Titratin Data 9. Initial Buret Reading Titratin #1 Titratin #2 Titratin #3 10. Endpint Buret Reading 11. Vlume f NaOH 12. ph f Vinegar after neutralizatin 109

110 Table C: Calculatins f the Mlarity f Acid Calculatins Number 14. Average Vlume f NaOH (ml) 15. Average Vlume f NaOH (L) 16. Mles f NaOH 17. Mles f Acid 18. Mlarity f Acid 110

111 Table D: Calculatins fr Weight/Vlume Percent f Acid & % Errr Calculatins Number Mles f Acid (cpy frm able C 17) Mlar Mass f Acid Grams f Acid Titrated Vlume f acid titrated (ml) Weight/Vlume % Percent Errr 111

112 Pstlab Questins 1. What ther indicatr can be used beside phenlphthalein can be used fr this experiment? 2. Other than vinegar, name a husehld prduct that is acidic and can be used in this experiment. Explain why yu have selected this prduct. 3. What is average [H3O+] f the vinegar slutin at the neutralizatin pint in the titratin prcess? 4. Can a slutin ever have a ph = 0? What des a ph =0 suggest abut the cncentratin f the acid? Can the ph ever be negative? What is the significance f a negative ph fr a slutin? 5. Cmplete the fllwing table. Assume that the slutin is 25 C and Kw = [H 3 O + ] [OH - ] ph Acidic Basic r Neutral i.e Basic A B C D Neutral Use 3 significant figures 112

113 A. Appendix Cmmn Cnversins Length SI Unit Meter (m) Vlume SI Mass SI Unit Kilgram Unit Cubic Meter (m 3 (kg) ) 1 m = 100 cm 1 L = 1000 ml 1 kg = 1000 g 1 m = 1000 mm 1 ml = 1 cm 3 1 kg = 2.20 lb 1 cm = 10 mm 1 L = 1.06 qt 1 lb = 454 g 1 km = mi 1 qt = 946 ml 1 mle = 6.02 x particles 1 in. = 2.54 cm (exact) 4 qt = 1 gal Density f water = 1.00 g/ml 16 z. = 1 lb Energy SI Unit Jule (J) R = LL aaaaaa = mmmmmm KK 62.4 LL mmmmmmmm mmmmmm KK 1 calrie = J 1 Mle gas = 22.4 L at STP Specific heat water = cccccc gg JJ gg = 1.00 Slubility Rules Sluble All cmpunds f Li +, Na +, K +, Rb +, Cs +, and NH4 + All cmpunds f NO3 and C2H3O2 Exceptins: Nne Nne Cmpunds f Cl, Br, I Ag +, Hg2 2+, Pb 2+ Cmpunds f SO4 2 Sr 2+, Pb 2+, Ca 2+, Ba 2+ These cmpunds generally d nt disslve in water (are insluble): Cmpunds f OH -, S 2-, CO3 2 and PO

114 Plyatmic Ins 114

115 Peridic Table 115