OTHS Academic Chemistry Lab Notebook

Transcription

1 Name Period 4 th Grading Period OTHS Academic Chemistry Lab Notebook I am among those who think that science has great beauty. A scientist in his laboratory is not only a technician: he is also a child placed before natural phenomena which impress him like a fairy tale. -Marie Curie-

2 Page Table of Contents Lab 1.. Snowman Challenge 3.. Types of Reactions 6.. S Mores 9.. Study of Stoichiometric Relationships Exploring Properties of Gases Boyle s Law Would you like your own pair of goggles? Order from Flinn Scientific, Models AP3306 and AP3309 are both approved. Lab Protocol: Electronic devices are not appropriate in a laboratory setting and may not be used or in sight during labs. Lab safety rules must be followed at all times. Negligence (not wearing goggles or closed toe shoes), not following instructions, purposeful horseplay, and harmful behavior will not be tolerated in the lab. Clean-up: In a chemistry lab, students are expected to take care of the equipment and lab stations. Each lab period, 10 points are allocated for lab clean-up. If the lab is left in disarray, 10 points will be deducted from the lab grade. Lost notebooks: Students are given one lab notebook each six weeks. If lost, students may print labs from the course website, but 5 points will be deducted for each occurrence. Late labs: 1 day late= Maximum 75, 2 days late= Maximum 50, 3+ days late= zero Unless specified otherwise, violation of lab protocol will result in a 20 point deduction from the lab grade and/or a discipline referral to the student s grade level principal.

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5 Lab: Types of Reactions Background: Chemical reactions can be classified into 5 basic categories to allow for prediction of products. They are: synthesis, decomposition, single replacement, double replacement and combustion. In today s lab you will investigate all of these types of reactions. In this lab, you will also identify three different gases based on your observations of their behavior. The information below will help you classify them: CO 2 gas: does not support combustion (extinguishes flame) O 2 gas: supports combustion (causes flame to burn brighter) H 2 gas: explosive Purpose: To observe chemical reactions, to predict the products of chemical reactions, and to identify three gases based on their behavior. Materials: 3-cm Mg strips 3% H 2 O 2 MnO 2 3 M HCl Vinegar 0.1 M BaCl M Na 2 SO M K 2 CrO 4 NaHCO 3 Tongs Watch glass Bunsen burner Test tubes Wooden splints Well plates Small beakers Graduated cylinders Procedure: A. (STATION 1) Combustion 1. Light the Bunsen burner. 2. Describe the flame of the Bunsen burner as an observation in the data table on line #1. Write the reactants and the products that represent the combustion of natural gas in the Bunsen burner. Natural gas is methane (CH 4 ). Synthesis 3. Obtain a 3 cm strip of magnesium. Grasping the magnesium with the tongs, hold it in the hottest part of the flame until it ignites. DO NOT LOOK DIRECTLY AT THE BURNING MAGNESIUM! Once the magnesium ignites, remove it from the flame and hold it over a watch glass on the lab counter. Record observations. 4. Write the reactants and the products that represent this reaction in the data table on line #2. Hint: the magnesium is reacting with oxygen gas when it burns. 5. Leave magnesium residue on the watch glass. B. (STATION 2) Decomposition 6. Measure 5 ml of H 2 O 2 (hydrogen peroxide) and pour into a test tube. 7. Using the wooden splint in the MnO 2 container, add a small amount of MnO 2 to the test tube (MnO 2 is a catalyst and will speed up the reaction). 8. Quickly light a wooden splint. After you have it burning for a few seconds, blow it out. Then immediately place the glowing splint into the mouth of the test tube, not in the liquid. Record your observations of the reaction and the gas behavior. Identify the gas. 9. Write the reactants and the products that represent the reaction in the data table on line #3. Remember to include the catalyst over the arrow. 10. Rinse tube in sink. 3

6 C. (STATION 3) Single Replacement 11. Measure 5 ml of 3 M HCl (STRONG acid---be careful!!!) and pour into a test tube. 12. Obtain a 3 cm strip of magnesium, fold it in half and add the folded magnesium strip to the test tube with the HCl. 13. As soon as you add the magnesium to the test tube, cap the tube with another tube inverted over it according to your teacher s instructions. Make sure the two mouths of the test tubes are pressed tightly together. Allow the reaction to proceed for about 25 seconds. 14. While one person is holding the tubes together, the other person should light a wooden splint. After the 25 seconds are up, move the inverted test tube away from the other tube, and while leaving it inverted, hold the lit splint right under the mouth. 15. Touch the outside of the test tube containing the acid and magnesium reaction. Record observations of the reaction and the gas behavior. Identify the gas. 16. Write the reactants and the products that represent the reaction in the data table on line # Allow tube to cool; then carefully dispose of contents in the sink and rinse with water. D. Double replacement (STATION 4) Part 1a 18. Obtain a well plate and add 5 drops of barium chloride to a well, and then add 5 drops of sodium sulfate to the same well. 19. Record observations of a chemical reaction taking place. 20. Write the reactants and the products that represent the reaction in the data table on line # Rinse well plate in sink and wipe out any remaining residue with a paper towel, if necessary. (STATION 5) Part 1b 22. Obtain a well plate and add 5 drops of barium chloride to a well, and then add 5 drops of potassium chromate (K 2 CrO 4 ) to the same well. 23. Record observations of a chemical reaction taking place. 24. Write the reactants and the products that represent the reaction in the data table on line # Rinse well plate in sink and wipe out any remaining residue with a paper towel, if necessary. (STATION 6) Part 2: **Double replacement followed by decomposition** 26. Add a small scoop of sodium bicarbonate (about the size of a blueberry) to a small beaker. Then add 5 ml of vinegar. Quickly light a wooden splint and hold the burning splint just inside the mouth of the flask. Record observations of the reaction and the gas behavior. Identify the gas. 27. Write the reactants and the products that represent the reaction in the data table on line #7. Write the second part of the reaction (decomposition) on line # Rinse flask in sink. *****CLEAN UP YOUR LAB AREA***** ****WASH YOUR HANDS***** 4

7 Name Per. Data Table for Lab: Types of Reactions OBSERVATIONS STATION 1: 1. Bunsen burner flame: 2. Magnesium and oxygen: CHEMICAL REACTION EQUATIONS 1. Combustion reaction: CH 4 + O 2 2. Synthesis reaction: Mg + O 2 STATION Decomposition reaction: Observation of gas behavior w/ flame: Circle: extinguishes, supports, explodes Identity of gas produced: STATION 3 4. Temperature: Circle: cold/hot H 2 O 2 (Hint: write the catalyst ABOVE the arrow and one product is H 2 O) 4. Single replacement: Mg + HCl Observation of gas behavior w/ flame: Circle: extinguishes, supports, explodes Identity of gas produced: STATION Double replacement part 1a: BaCl 2 + Na 2 SO 4 STATION Double replacement part 1b: BaCl 2 + K 2 CrO 4 STATION 6 7. Temperature: Circle: cold/hot Observation of gas behavior w/ flame: Circle: extinguishes, supports, explodes Identity of gas produced: 7. Double replacement part 2: NaHCO 3 + HC 2 H 3 O 2 8. Decomposition (of H 2 CO 3 that was formed above in #7): H 2 CO 3 (Hint: one product is H 2 O) 5

8 S mores Reactant Quantities by Group Number Group # 1 Mm 15 Gc 8 Hc 6 Group # 2 Mm 12 Gc 12 Hc 5 Group # 3 Mm 12 Gc 12 Hc 6 Group # 4 Mm 21 Gc 10 Hc 4 Group # 5 Mm 15 Gc 8 Hc 5 Group # 6 Mm 18 Gc 10 Hc 4 Group # 7 Mm 12 Gc 10 Hc 5 6

9 S Mores Lab Introduction: In most chemical reactions, one of the reactants can be identified as the limiting reactant. It is the reactant that is the first to run out as the reaction proceeds. It is called limiting because it limits the amount of product(s) that can be made. The other reactant(s) will have some left over ( in excess ), so we call it/them the excess reactant(s). In this lab, we make s mores to demonstrate the principle of limiting and excess reactants. Materials: graham crackers (Gc) Hershey chocolate bars (Hc) Mini marshmallows (Mm) hot plates spatulas aluminum pans and aluminum foil Procedure: 1. Wash your hands. 2. Write your lab group/station # here: # 3. The following is the balanced equation for the formation of 1 s more: (2 graham cracker halves (squares), 1 Hershey chocolate square, and 3 mini marshmallows) 2 Gc + 1 Hc + 3 Mm 1 Gc 2 HcMm 3 (s more) 4. Look at the previous page. Based on your lab group s number, determine your ingredients and record the quantities needed below: #Mm = #Gc = #Hc = 5. Calculate the number of s mores you can make, given the amounts listed in #4. 6. Identify your limiting reactant by its chemical symbol Circle: Mm, Gc, Hc 7. Identify your excess reactants by their chemical symbols and the # remaining: Excess reactant #1: Mm, Gc, Hc # remaining Excess reactant #2: Mm, Gc, Hc # remaining 8. Line your aluminum pan with aluminum foil. Assemble the s mores according to the equation in #3 above. Place the s mores on the foil and heat pan on hot plate ON LOW. Flip once with spatula. ***CAUTION: Do not turn up hot plate, or graham crackers will burn!*** 9. Enjoy s mores and clean up lab area. Crumbs on counter should go in the trash, not the floor...throw away foil but keep aluminum pans. 10. Answer conclusion questions on the next page. 7

10 Name: Period: S Mores Lab Student Sheet Questions: 1. Write, in your own words, a general definition of a limiting reactant. 2. A group of students has 33 mini marshmallows (Mm), 25 graham cracker squares (Gc), and 14 Hershey s chocolate squares (Hc). How many s mores can they make? SHOW WORK AND BOX ANSWER! a. What is the limiting reactant? (Circle): marshmallows, graham crackers, chocolate b. What are the excess reactants and how many pieces of each are left over? Excess reactant #1 (Circle): marshmallows, graham crackers, chocolate # remaining Excess reactant #2 (Circle): marshmallows, graham crackers, chocolate # remaining 3. You have a pile of marshmallows (Mm) with mass 60.g, a stack of graham crackers (Gc) with mass 74 g, and a stack of chocolate (Hc) with mass 72 g. Using the above masses and conversion factors from below, determine how many s mores you can make (Hint: these are two-step conversions and you can get the second conversion factor from the balanced equation in procedure #3; see below for example). Use dimensional analysis and show work below: Given conversion factors: 1 Mm = 0.60 g (this is similar to 1 mole of O = g) 1 Gc = 7.4 g 1 Hc = 3.6 g EXAMPLE with Mm: Mm: 60. g Mm x 1 Mm x 1 Gc 2 HcMm 3 (s more) = 33 s mores 0.60 g Mm 3 Mm Gc: Hc: 4. Consider the reaction between magnesium and hydrochloric acid below, in which Mg is the limiting reactant: Mg (s) + 2 HCl (aq) MgCl 2 (aq) + H 2 (g) (limiting) (excess) After the reaction is complete, which substances will be left over? Hint: think about what was left over in the s mores reaction after the limiting reactant ran out. Circle your answer(s): Mg HCl MgCl 2 H 2 8

11 Lab: Study of Stoichiometric Relationships Purpose: (1) Identify the limiting reactant in the chemical reaction between iron and copper (II) sulfate, (2) determine the mole ratios of reactants and products and write a balanced equation for the reaction, and (3) calculate the percent yield of copper. Materials: Digital balance Weigh boat Filter paper 250 ml beaker Stirring rod Funnel Spatula 100 ml grad. cylinder Flask for filtrate Wash bottle/dist. water Chemicals: Iron filings Copper (II) sulfate pentahydrate Procedure: Day 1 1. Obtain a 250 ml beaker. Place the beaker on the balance and zero it out. Add approximately 4 g of copper (II) sulfate and record the exact mass in your data table. 2. Add 70.0 ml of distilled water to a 100 ml graduated cylinder. Add the water to the beaker and stir the solution until all of the solid has dissolved. 3. Obtain a weigh boat. Place the weigh boat on the balance and zero it out. Add approximately 1 g of iron filings and record the exact mass. 4. Describe the appearance of your two reactants in the data table. 5. Add the iron filings to the CuSO4 solution. Rinse the weigh boat with a small squirt of distilled water to transfer any remaning iron to the beaker. 6. Stir the mixture and allow it to react for 10 minutes. 7. While the reaction is proceeding, obtain a piece of filter paper and use a pencil to write your initials and class period on the edge of the paper. Determine the mass of the filter paper and record. (CONTINUED) 9

12 8. After the 10 minutes has passed, describe the appearance of the materials in the beaker. Look carefully for evidence of any leftover reactant (Fe or CuSO4). 9. Dampen a funnel with water so that the filter paper will stick to it. Fold the filter paper into fourths and place it in the funnel as instructed by your teacher. Place the funnel tip into a flask to catch the filtrate (liquid that drips out of the funnel). 10. Swirl the beaker containing the reaction mixture and slowly pour into the funnel. Do not allow the solution to rise over the top edge of the filter paper. All of the solid must be transferred to the filter paper. Use the wash bottle with distilled water to aid in the transfer of solid. Continue filtering until all of the liquid has passed through the paper into the flask. 11. Obtain a piece of paper towel. Carefully remove the filter paper from the funnel, and place on the paper towel. Gently unfold the filter paper, being careful not to tear it, and use a stirring rod to carefully spread out the wet solid copper. Wash your hands! 12. Place the filter paper in an area designated by your teacher. 13. Dispose of the filtrate in the sink, clean equipment, and clean up your lab area. Wash your hands! Procedure: Day Obtain your dried filter paper and solid copper product. Weigh the paper with copper on the balance and record. 15. Subtract the mass of the paper and record the mass of the copper. 16. Dispose of the filter paper and solid in the trash can. 17. Clean up your lab area and wash your hands! 10

13 Name Per. Student Sheet: Study of Stoichiometric Relationships Data Table 1. Mass of CuSO4 2. Mass of Fe filings 3. Observations of reactants before reaction Fe: CuSO4 solution (in water): 4. Observations of beaker contents when reaction is complete 5. Mass of filter paper 6. (DAY 2) Mass of dried filter paper and Cu product 7. (DAY 2) Mass of Cu product (experimental yield) Questions and Calculations 1. A product of this reaction (besides copper) is either iron(ii)sulfate or iron(iii)sulfate. Complete and balance the equations below with each of these products: (you will determine which is correct later) A. Fe + CuSO4 + Cu B. Fe + CuSO4 + Cu 2. Which of the reactants, the iron or the copper (II) sulfate, was the limiting reactant? Which was in excess? You must do this by lab observations, since you don t yet know which of the above equations is the correct one. Hint: what color was the filtrate (liquid) in the flask? This will help you determine which reactant still remains (excess). Limiting = Excess = 3. (a) Convert the mass of the limiting reactant to moles of limiting reactant: (b) (DAY 2) Convert the mass of copper product (line 7 of data table) to moles of copper product: (c) (DAY 2) What is the mole ratio (in whole numbers) of the limiting reactant to copper? (d) (DAY 2) Which equation from #1 does this match, A or B? 4. (DAY 2) Starting with the mass of the limiting reactant, calculate the theoretical yield of copper using stoichiometry. 5. (DAY 2) Calculate the percent yield of copper, using your theoretical yield from #4 above and your experimental yield from line 7 of your data table. The formula for % yield is in your notes. 11

14 Exploring Properties of Gases Introduction In this laboratory activity, you will perform a variety of experiments that illustrate some properties of air. Carefully read through the procedure before you start this activity. Decide what you think will happen at each of the seven laboratory stations, and write down your predictions. Procedure Each station will have an individual set of instructions. Read all the instructions at that station before you start that experiment. Be sure to write your predictions before you try the experiment as well. After you perform your experiment, record your observations and clean up that station before moving to the next station. Questions Station #1: Mass of Air Does air have mass? How does this experiment show that? Station #2: Paper under Water Explain why the paper did not get wet. Station #3: Bottle with a Hole Explain why it is necessary to have the cap off in order for the water to continuously flow out of the hole in the bottle. Station #4: The Plunge Explain how the can gets crushed. Hint: Think about what happens to the steam in the can after it is submerged in the ice water. Station #5: Balloon in Vacuum Pump What happened to the volume of the balloon after pumping? Why? What happened to the marshmallow after pumping? Why? Station #6: The Leaky Straw Explain why the straw with the holes does not work. Station #7: The Cartesian Diver Explain why the diver sinks when you squeeze the bottle. 12

15 Boyle s Law: Pressure-Volume Relationship in Gases (with Vernier LabQuest) The primary objective of this experiment is to determine the relationship between the pressure and volume of a confined gas. The gas we will test is air, and it will be confined in a syringe connected to a Gas Pressure Sensor (see apparatus below). When the volume of the syringe is changed by moving the piston, a change occurs in the pressure exerted by the confined gas. This pressure change will be monitored using a Gas Pressure Sensor. It is assumed that temperature will be constant throughout the experiment. Pressure and volume data pairs will be collected during this experiment and then analyzed. From the data and graph, you should be able to determine what kind of mathematical relationship exists between the pressure and volume of the confined gas. Historically, this relationship was first established by Robert Boyle in 1662 and has since been known as Boyle s law. OBJECTIVES Figure 1 In this experiment, you will Use a Gas Pressure Sensor and a gas syringe to measure the pressure of an air sample at several different volumes. Determine the relationship between pressure and volume of the gas. Describe the relationship between gas pressure and volume in a mathematical equation. Use the results to predict the pressure at other volumes. MATERIALS LabQuest LabQuest App Vernier Gas Pressure Sensor 20 ml gas syringe PROCEDURE 1. Prepare the Gas Pressure Sensor and an air sample for data collection: a. Connect the Gas Pressure Sensor to LabQuest and choose File New. b. Disconnect the syringe from the Gas Pressure Sensor c. Move the piston of the syringe until the front edge of the inside black ring (indicated by the arrow in Figure 1) is positioned at the 10.0 ml mark. d. Attach the 20 ml syringe to the valve of the Gas Pressure Sensor. 2. Set up the data-collection mode: a. On the Home screen, tap Mode (located on top right of screen). b. Click on the drop-down menu and change the mode to Events with Entry. c. Change the Name to Volume, click done. d. Change Units to ml, click done again, and select OK. 13

16 3. To obtain the best data possible, you will need to correct the volume readings from the syringe. Look at the syringe. Its scale reports its own internal volume; however, that volume is not the total volume of trapped air in your system since there is a little bit of space inside the pressure sensor. ***To account for the extra volume in the system, you will need to add 0.8 ml to your syringe readings. For example: with a 5.0 ml syringe volume, the total volume would be 5.8 ml. It is this total volume that you will need for the analysis. 4. You are now ready to collect pressure and volume data. It is easiest if one person takes care of the gas syringe and another enters volumes. Record pressure readings after data collection, not during. 5. Start data collection: a. Tap the green arrow on the bottom left corner of the screen. b. Move the piston on the syringe so the front edge of the inside black ring (see Figure 1) is positioned at the 5.0 ml line. c. Hold the piston firmly in this position until the pressure value displayed on the screen stabilizes. d. Tap Keep and enter 5.8, the gas volume (in ml) on the screen, even though you stopped the piston at 5.0 ml. Remember, you are adding 0.8 ml to the volume of the syringe for the total volume. e. Select OK to store this pressure-volume data pair. 6. Continue this procedure using syringe volumes of: 10.0, 12.5, 15.0, 17.5, and 20.0 ml. 7. Stop data collection: a. Tap the red square on the bottom left corner of the screen. b. When data collection is complete, a graph of pressure vs. volume will be displayed. To examine the data pairs on the displayed graph, tap any data point. c. As you tap each data point, the pressure and volume values are displayed to the right of the graph. d. Record the pressure and volume data values in your data table below. DATA TABLE Volume (ml) 5.0 ml 10.0 ml 12.5 ml 15.0 ml 17.5 ml 20.0 ml Pressure (kpa) Constant, k (P x V) On the Home screen, select File New Discard so the LabQuest is ready for the next group. 14

17 CALCULATIONS AND CONCLUSIONS 1. On the next page, make a graph of pressure vs. volume. The volume goes on the x axis (independent variable) and the pressure goes on the y axis (dependent variable). Pressure is dependent on volume and will change because the volume changes. Divide the axes into appropriate increments and plot the data in your data table. Connect the data points with a best fit line or curve. 2. If the volume is doubled from 5.0 ml to 10.0 ml, what does your data show happens to the pressure? (Circle): Increased/decreased by (Circle): 1x / 2x / 3x / 4x 3. If the volume is tripled from 5.0 ml to 15.0 ml, what does your data show happened to the pressure? (Circle): Increased/decreased by (Circle): 1x / 2x / 3x / 4x 4. From your answers to questions #2 and #3, and the shape of the curve in the plot of pressure versus volume, do you think the relationship between the pressure and volume of a confined gas is: (Circle): direct or inverse? Explain: 5. Look at your graph on the next page. Based on your data, if the volume of the syringe was increased to 40.0 ml, what would you expect the pressure to be? (Circle): Should increase/decrease to Explain: 6. Look at your graph on the next page. Based on your data, if the volume of the syringe was decreased to 2.5 ml, what would you expect the pressure to be? (Circle): Should increase/decrease to Explain: 7. Calculate k for each of your data points (k is the product of P x V). Record the value in the 3rd column of your data table. Note: good data may show some minor variation, but the values for k should be relatively constant. Why might your data not show k as constant? Explain: 8. You fill a balloon with helium in downtown Colorado Springs (elevation 5,740 ft). You tie the balloon to your backpack and hike all the way to the top of Pike s Peak (14,110 ft). Based on your lab results, since pressure decreases at high altitudes, what do you expect will happen to the volume of your balloon? (Circle): increase/decrease volume of the balloon Explain: 9. a) The scenario above is not truly Boyle s Law, because the temperature is not constant. What effect do you think the cooler temperature on Pike s Peak will have on the balloon? (Circle): increase/decrease volume of balloon b) You have determined the relationship between pressure and volume in question number 4. Based on your answer for question 9a, what do you think the relationship is between temperature and volume? (Circle): direct or inverse? Explain: 15

18 16 Free Plain Graph Paper from