Stoichiometry in the Home.. STOICHIOMETRY!!.and Stoichiometry in the chemistry lab

Transcription

1 Stoichiometry in the Home.. STOICHIOMETRY!!.and Stoichiometry in the chemistry lab 1

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3 Chemistry in the Community Stoichiometry This is a challenging unit. To succeed, keep up with all the work. Learn it, don t just do it. Ask questions and work hard. Answers to Packet Pages Assigned for Homework are in the back of the packet! Date In-Class Assignment Homework R 10/29 Types of Reactions Test F 10/30 Happy Halloween M 11/2 Go over test What is a Mole? Molar Mass Packet p 9 Mole Project due! Mole Day Party!...Mole Songs and Cartoons! Go over pkt p 10 Molar Conversions pkt p T 11/3 Go over pkt p 13 Percent Composition pkt p 15 Begin Percent Composition pkt p 16 #1-2 Complete Mole Day Project! Molar Mass pkt p 10 Molar Conversions Homework pkt p13 CONFUSED?? See Camtasia Video on SHAREPOINT site. Percent Composition pkt p 16 #3-4 Molar Mass pkt p 14 (if you need extra practice) Study for Quiz! On Molar Mass, Molar Conversions, and % Composition! W 11/4 R 11/5 PT Conferences 6-9pm F 11/6 Non- Attendance Mole Conversion/% Composition Quiz! Work on S More Chemistry Questions pkt p #1-4 Camp Stoichiometry!!! S MORES!! Pkt p No School: PT Conferences Day M 11/9 Mole Island! Pkt p 21 Mole-Mole Stoichiometry Pkt p T 11/10 Go over p 24 Mass-Mole Stoichiometry Mass-Mass Stoichiometry Pkt p 25 Complete pkt p Read Sections C.4, C.6-C.7 textbook p for a review for tomorrow s quiz S More Chemistry pkt p 17-18, question 1-4 Pkt p 24 CONFUSED?? See Camtasia Video on SHAREPOINT site. Complete pkt p

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5 W 11/11 Late Start Day Questions on pkt p 26-28? Limiting Reactants Pkt p Pkt p CONFUSED?? See Camtasia Video on SHAREPOINT site R 11/12 Go over p Excess Reactants pkt p Begin p F 11/13 Go over pkt p Review over material Complete Pre Lab pkt p 41 in Background Info #1-3 Finish pkt p Complete pkt p 47 #1-2 CONFUSED??See Camtasia Video on SHAREPOINT site. SHOES FOR TOMORROW! M 11/16 LAB: Limiting Reactant Lab p Day 1 Lab Questions 1,2,5,6 SHOES! T 11/17 Parent Participatio n Day LAB: Limiting Reactant Lab p Day 2 Work on Stoich Extra Practice Problems p Finish lab and turn in (NO CONCLUSION!) Study for Test W 11/18 R 11/19 Cu Unlimited Overview Decide on Class Managers Questions/Review for test TEST: Section C.4-C.6 and Stoichiometry Study for Test! Cu Unlimited Manager Meeting Monday before school or after school on November 23rd! 5

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7 Chemistry Name: Period: Stoichiometry Objectives Checklist My action plan to help me improve my learning includes: Review labs, notes, packet and activities. Use the calendar to make sure everything is reviewed. Have a family member or friend quiz me orally. Meet with my teacher in the morning/afterschool for extra help. Use the magic calculator online to check your calculation answers to appropriate labs. Complete and review homework problems by reworking them and NOT just looking at them. Use Objective Checklist throughout unit to assess understanding Ask and answer questions during class. Start studying early! (Not just the night before the test.) Re-read or review all assigned sections from the book. Do online practice quizzes available through class website or through internet. Find a study buddy from Chemistry who understands the material and I can work well with. Use Objective Checklist as a study guide Use this checklist as your personal guide to assess your level of readiness for quizzes and the unit test. Circle the descriptor that best describes how you feel about your mastery of each objective. NOTE: IF IT IS NOT A, YOU PROBABLY ARE NOT READY FOR THE QUIZ/TEST!!!!! = I get it? = I need more practice/review! = I need to get help During Unit Before Test (An asterisk indicates an overarching theme from a past unit!) I feel confident that I?!?! 1. understand the mole concept and Avogadro s number.?!?! 2. understand and can calculate Molar Mass.?!?! 3. can perform Molar conversions using mass, moles and particles.?!?! 4. Can perform basic stoichiometry conversions including: mole to mole, gram to gram, gram to mole and mole to gram from given data or lab date.?!?! 5. Understand and identify limiting reactant, excess reactant and theoretical yield including in a lab situation.?!?! 6. Can calculate theoretical yield from given data or lab data.?!?! 7. Can calculate moles and/or grams of excess reactant remaining from given data or lab data.?!?! 8. Can calculate percent composition of a compound. Check off the study skills you USED to move from? or! to while studying for the test. 7

8 I have carefully self-assessed my work during this unit and have taken steps to get my questions answered before the quiz/test. Student Signature: Parent Signature: Date: 8

9 List some examples of counting units: The Mole!! What is a chemist's counting unit? Why do we need a chemist's counting unit? Ex: the decomposition of water: 2 H2O (l) 2 H2 (g) + O2 (g) One dozen water molecules = One mole of water molecules = How BIG is a mole? If we want to decompose 2 moles of H2O in the lab, how are we going to count out 2 moles of H20 molecules? WE CAN'T!!!!! Molar Mass; What is the Molar mass of? 1 mole Ag = 1 mole of K = 1 mole H2O = Calculating Molar mass of compounds: H2O: Ca (NO3)2 9

10 Molar Mass Homework Calculate the Molar Mass of each compound. Be sure to SHOW ALL WORK!!! 1. Nitrogen gas: N2 2. potassium oxide: K2O 3. magnesium sulfate: MgSO4 4. ammonium sulfide: (NH4)2S 5. barium chloride: 6. calcium phosphate: 10

11 Molar Conversions Two conversion factors: 1 mole = 6.02 x (atoms/molecules/formula units) 1 mole = molar mass (in grams) calculated from Periodic Table REVIEW of conversions (aka T-charts or Factor-Label Method) 1. Convert 55 eggs into dozen. 2. Convert 43 cups into pints. EXAMPLES OF MOLAR CONVERSIONS: 1. How many formula units* are in 3.5 mol of NaCl? 2. How many moles of Ag are in 4.78 x atoms of Ag? 3. How many grams are in 4.20 moles of H2O? *Formula units are particles (atoms, molecules, ions, etc.) 11

12 Two conversion factors: 1 mole = 6.02 x (atoms/molecules/formula units) 1 mole = molar mass (in grams) calculated from Periodic Table g of Mn is equal to how many moles? 5. How many formula units of NaCl are present in g? 6. How many grams of CO2 are present in 5.2 x molecules of CO2? 12

13 Molar Conversions HOMEWORK!!!! Two conversion factors: 1 mole = 6.02 x (atoms/molecules/formula units) 1 mole = molar mass (in grams) calculated from Periodic Table YOU MUST SHOW ALL WORK FOR ANY CREDIT! Use proper sig figs and units! 1. How many moles of Silicon are in 6.2 x atoms of Si? (0.0010) 2. How many molecules of P2O5 are in 0.15 moles of P2O5? (9.0 x ) 3. How many moles are in 16.0 grams of Cu? (0.252) 4. What is the mass of 5.00 moles of CO2? (220.) 5. How many magnesium atoms are present in 5.00 g of magnesium? (1.24 x ) 13

14 Molar Conversions CLASSWORK PRACTICE Two conversion factors: 1 mole = 6.02 x (atoms/molecules/formula units) 1 mole = molar mass (in grams) calculated from Periodic Table YOU MUST SHOW ALL WORK FOR ANY CREDIT! Use proper sig figs and units! 1. What is the mass in grams of 0.25 moles of H2O? (4.5) 2. How many formula units are in moles of Mg3(PO4)2? (1.984 x ) 3. How many moles of calcium chloride are in a 22.5 g sample of calcium chloride? (0.203) 4. What is the mass in grams of 5.2 x calcium atoms? (3.5) 5. How many molecules are in 11.5 g of NH3? (4.06 x ) 6. How many moles of sodium hydroxide are in 1.00 kg of sodium hydroxide? (25.0) 14

15 Percent Composition by Mass Background: How would you calculate the percentage of females in our class? Show your work. How would you calculate the percentage by mass of females in our class? PERCENT COMPOSITION BY MASS OF CHEMICAL COMPOUNDS: EX: What is the percent by mass of the elements in water? EX: If a 9.87 g sample of an ore contains 3.29 g of the mineral chalcopyrite (CuFeS2), what percent by mass of the mineral is in the ore? EX: what is the percent by mass of the elements in the mineral chalcopyrite (CuFeS2)? 15

16 Percentage Composition Worksheet Give the % composition of all elements in these compounds. Show all work! 1. ammonium sulfite 2. aluminum acetate 3. sodium bromide 4. copper (II) hydroxide 16

17 S'More Chemistry An Introduction to Stoichiometry You have spent a lot of time studying the various types of reactions that can occur in chemistry. You have also become experts in balancing chemical equations. In this activity, you will be introduced to simple stoichiometry. Stoichiometry is the branch of chemistry that deals with calculations that determine the quantities of substances that enter into and are produced by a chemical reaction. Stoichiometry is very similar to following a recipe specific amounts of ingredients (reactants) are needed to make a specific amount of a delicious meal (products). Complete the following worksheet. Bring it to your teacher to check your answers. When all answers are correct (with appropriate work being shown), you may make a S more!!! In stoichiometry, you must always start with a balanced equation. We will use the following balanced equation (recipe): 2 Gc + 1 M + 3Cp 1Sm Where: Gc = graham cracker Cp = chocolate pieces M = marshmallow. Sm = S'more 1. Notice to make this recipe you have 6 pieces (reactants) to the left side of the arrow and 1 piece (product) to the right. This is supposed to be a balanced equation, so how can 6 = 1? 2. If each student in class is to make one S'more and I have 20 students, how much of each ingredient will I need? EXPLAIN your logic. 3. How many S'Mores can you make from these combinations? 2 Gc + 1 M + 3Cp Sm 4 Gc + 2 M + 6 Cp Sm 10 Gc + 5 M + 15 Cp Sm 17

18 4. If you had 4 graham crackers, 1 marshmallow and 9 chocolate pieces in your cupboard, how many complete S'Mores could you make? What (and how many) leftover ingredients would you have? EXPLAIN YOUR LOGIC. 5. You can (AND WILL!!!) solve questions like #4 using T-Charts and the following format. 1) For each ingredient, determine how much of the ingredient is needed to make the product (1 S'More). Also determine the relationship between the quantities of ingredients needed. Write these as equalities. a. 2 Gc needed per S more 2 Gc = 1 Sm b. 1 M needed per S more 1M = 1 Sm c. 3 Cp needed per S'More 3 Cp = 1 Sm d. 2Gc per 1M per 3 Cp 2 Gc = 1M = 3Cp These equalities will be used as your conversion factors in the T charts 2) Using a separate T-chart for each ingredient, determine how many S'Mores can be made from the amount you have in your cupboard (when dealing with each ingredient separately, you make the assumption that you have enough of all other ingredients present). 1 Sm 4 Gc x = 2 Sm (2 complete S'Mores can be made) 2 Gc This calculation tells us that 2 S'Mores can be made with 4 graham crackers (assuming we had all the Marshmallows and Chocolate pieces we needed). 1 Sm 1 M x = 1 Sm (1 complete S'More can be made) 1 M This calculation tells us that 1 S'More can be made with 1 marshmallow (assuming we had all the Graham crackers and Chocolate pieces we needed). 1 Sm 9 Cp x = 3 Sm (3 complete S'Mores can be made) 3 Cp This calculation tells us that 3 S'Mores can be made with 9 chocolate pieces (assuming we had all the Marshmallows and Graham crackers we needed). 3) Determine the maximum number of S'mores that can be made. This is called the theoretical yield. We only have enough ingredients to make 1 complete S'More, although we have enough chocolate pieces to make 3 S Mores and graham crackers to make 2 S Mores. Therefore our theoretical yield is only 1 S More. 4) Determine which ingredient limits us to the maximum number of S'Mores we can make. (The ingredient (reactant) that gets used up first and limits the maximum amount of product that can be made is known as the limiting reactant). The limiting reactant is the marshmallows because that is the ingredient that gives us the least amount of product from step #2. 18

19 5) Determine how much of the other reactants are left over. These are called the excess reactants. This can be determined by figuring out how much of each reactant is USED to make the maximum product, and then subtracting it from the amount you started with. We determined we can make 1 S more. First figure out how many Gc are needed to make this. 2 Gc 1 Sm x = 2 Gc will be used 1 Sm 4 Gc (started with) 2 Gc (used up) = 2 Gc remaining Do the same for the chocolate pieces (these were not all used up either). 3 Cp 1 Sm x = 3 Cp will be used 1 Sm 9 Cp (started with) 3 Cp (used up) = 6 Cp remaining These Gc and Cp s remaining are the excess reactants the leftover ingredients 6) Use the format from Question #5 to do the following. YOU MUST SHOW ALL WORK WITH PROPER UNITS AND SIGNIFICANT FIGURES. a. If you are given 2 graham crackers, 5 marshmallows and 6 chocolate pieces., determine; The theoretical yield of S'Mores The limiting reactant and the excess reactants The quantity of the excess reactants remaining. 19

20 b. If you are given 12 graham crackers, 15 marshmallows and 6 chocolate pieces, determine; The theoretical yield of S'Mores The limiting reactant and the excess reactants The quantity of the excess reactants remaining. c. If you are given 156 graham crackers, 310 marshmallows and 66 chocolate pieces, determine; The theoretical yield of S'Mores The limiting reactant and the excess reactants The quantity of the excess reactants remaining. You are now ready to bring this sheet to your teacher for checking!! After it is checked, go to a Bunsen burner and obtain a wooden splint and S'More ingredients. You can use a paper towel as a clean surface for your ingredients. 1. Break your graham cracker into 2 pieces. Place the chocolate onto one of the graham crackers. 2. Roast your marshmallow over the Bunsen burner DO NOT MELT IT! 3. Quickly place the marshmallow onto the chocolate pieces and cover it with your second graham cracker. 4. Wait for it to cool and ENJOY! 20

21 Stoichiometry Island Diagram 21

22 Basic Stoichiometry Define stoichiometry in your own words. What is the first thing you always need before starting a stoichiometry problem? MOLE to MOLE Stoichiometry examples: (one-step T-chart) 1. Balance the following equation: N2 (g) + H2 (g) NH3 (g) 2. Write the molar ratio below the equation. 3. If we react 0.87 mol of nitrogen with an excess of hydrogen, how many moles of NH3 will be formed? 4. If we react mol of hydrogen how many moles of nitrogen do we need? 5. If you produced 3.92 moles of NH3, how many moles of hydrogen must have reacted? 22

23 MOLE to MOLE Stoichiometry CLASSWORK Answer questions 1-3 using the following reaction. DON'T FORGET TO BALANCE IT FIRST! CH4 (g) + O2 (g) CO2 (g) + H2O (l) 1. If we react 4.29 moles of CH4 with an excess of oxygen, how many moles of CO2 will be formed? 2. If we react 18.7 moles of oxygen, how many moles of H2O will be formed? 3. If we react mole of CH4, how many moles of O2 do we need? Answer questions 4-6 using the following reaction. DON'T FORGET TO BALANCE IT FIRST! P (s) + O2 (g) P2O5 (s) 4. How many moles of P2O5 will be produced from 0.4 moles of O2? 5. If we react 3.2 moles of P, how many moles of O2 do we need? 6. How many moles of P2O5 will be produced from 0.21 moles of P? 23

24 Given the following reaction: Mole-Mole Stoichiometry KClO3 KCl + O2 1. If we start with moles of KClO3 how many moles of KCI would be produced? (HINT: balance equation first!) 2. If 3.68 moles of KCl are produced, how many moles of O2 must we have started with? 3. If moles of O2 is produced, how many moles of KCl will be produced? 4. If moles of KClO3 are used in this reaction, how many moles of O2 would be produced? REVIEW QUESTION!!!! 5. How many grams are in moles of O2? 24

25 Classwork Mass - Mole /Mole - Mass Stoichiometry Step 1: Balance!!! H2 (g) + O2 (g) H2O (g) 1. How many moles are needed of oxygen to completely react with 6.02 grams of hydrogen? 2. How many moles of water is produced if we react 502 grams of oxygen with plenty of hydrogen? 3. If 24.3 moles of water were produced, how many grams of hydrogen were needed for this reaction to occur? Mass - Mass Stoichiometry Step 1: Balance!! Li (s) + ZnCl (aq) Zn (s) + LiCl (aq) 4. How many grams of lithium are needed to completely react with grams of zinc chloride? 5. How many grams of zinc can be made if we have 82.3 grams of lithium and unlimited ZnCl2? 6. How many grams of lithium chloride can be produced if you started with 1,235 grams of lithium and unlimited zinc chloride? 25

26 Mass - Mole / Mole - Mass Stoichiometry CH4 + O2 CO2 + H2O 1. How many grams of oxygen do you need to completely bum moles of methane (CH4)? (1697) 2. How many moles of carbon dioxide (CO2) are produced if 132 grams of methane (CH4) burns in the presence of excess oxygen? (8.22) 3. How many grams of water are produced when 6.25 moles of oxygen reacts with excess methane? (113) Al + O2 Al2O3 Mass - Mass Stoichiometry 1. How many grams of aluminum are needed to react completely with 8.5 grams of oxygen? (9.6) 2. How many grams of Aluminum oxide are produced when 192 grams of aluminum reacts with excess oxygen? (363) 3. If grams of oxygen reacts with excess aluminum, how many grams of aluminum oxide would be produced? (138.04) 26

27 Stoichiometry Homework Balance the following equations and answer the questions 1. KClO3 (s) KCl (s) + O2 (g) a. How many moles of O2 can be produced by letting moles of KClO3 react? 2. K + Cl2 KC1 a. How many grams of KCl is produced from 2.50 g of K and excess Cl2? b. How many grams of KCl is produced from 1.35 moles of Cl2 and excess K? 3. Given the following equation: Na2O (s) + H2O (l) + NaOH (aq) a. How many moles of NaOH is produced from 121 grams of Na2O? b. How many grams of Na2O are required to produce 160 grams of NaOH? 27

28 4. Write out and balance the following reaction. Include states of matter: Solid sodium chlorate decomposes into solid sodium chloride and oxygen gas. a moles of sodium chlorate will produce how many moles of oxygen? b. How many moles of sodium chloride are produced when 80.0 grams of oxygen are produced? 5. Write out the complete balanced equation including states of matter. Molten iron and carbon monoxide gas (CO) are produced in a blast furnace by the reaction of solid iron (III) oxide and solid coke (pure carbon). a. If 3.28 moles of iron is produced, how many grams of pure carbon did we start with? b. If 25.0 kilograms of pure iron (III) oxide is used, how many kilograms of iron can be produced? 28

29 LIMITING REACTANT CALCULATIONS Limiting reactants are vital for the human body (enzymes / diet). We have discussed limiting reactants previously during our S'more lab. In your own words define the following using your experience in the S'more lab: Theoretical Yield: Limiting Reactant: Excess Reactant: Recall: 2 Gc + 1 M + 3 Cp 1 Sm Given 4 graham crackers, 5 marshmallows and 9 chocolate pieces what is the theoretical yield of S'mores? (Recall: you must use T-charts to predict the maximum you can produce for each and then compare) Label the following on your above work: 1. Box your theoretical yield and label it TY. 2. Circle the limiting reactant and label it LR. 3. Circle the excess reactants and label them ER. We will calculate the amount in excess tomorrow. For today this is all we are going to do. 29

30 Now let's try it with chemicals: Step 1: Predict and balance the following reaction when glucose (C6H12O6) burns during cellular respiration. C6H12O Kcal (energy) 1. If you have 10 moles of glucose and 12 moles of oxygen, a. How many moles of carbon dioxide would be produced? You know this is a limiting reactant problem because you have multiple givens from your reactants. b. Label the theoretical yield, limiting reactant and excess reactant. 2. If you have 10.0 moles of glucose and 12 moles of oxygen a. How many grams of carbon dioxide can be produced? b. Label the theoretical yield, limiting reactant and excess reactant. 30

31 3. Supplemental glucose tablets list the amount of glucose in grams, not moles. Some people take these supplements prior to their workout. a. If one tablet has 120 g of glucose and during their workout 50. g of oxygen were available, how many moles of carbon dioxide would be produced during the workout? b. Label the theoretical yield, limiting reactant and excess reactant. 4. If one tablet has 120 g of glucose and during their workout 50. g of oxygen were available a. How many moles of carbon dioxide would be produced? b. Label the theoretical yield, limiting reactant and excess reactant. 31

32 LIMITING REACTANT CALCULATIONS HOMEWORK Solid Iron (III) oxide reacts with carbon monoxide gas to produce iron metal and carbon dioxide gas according to the following equation. Fe2O3 (s) + CO (g) Fe (s) + CO2 (g) 1. If 180 moles of iron (III) oxide and 110 moles of CO are mixed together, a. How many moles of iron would be produced? Don't forget to balance the equation before you start. b. Label the theoretical yield, limiting reactant and excess reactant. 2. If 52 grams of iron (III) oxide and 52 grams of carbon monoxide are mixed together, a. How many grams of carbon dioxide can be produced? b. Label the theoretical yield, limiting reactant and excess reactant. 32

33 Fe2O3 (s) + CO (g) Fe (s) + CO2 (g) 3. If you have grams of carbon monoxide that is mixed with 5.34 moles of iron (III) oxide, a. How many moles of iron can be produced? b. Label the theoretical yield, limiting reactant and excess reactant. 4. If you have 5.32 grams of carbon monoxide that is mixed with 2.94 grams of iron (III) oxide, a. How many grams of carbon dioxide can be made? b. Label the theoretical yield, limiting reactant and excess reactant. 33

34 EXCESS REACTANT CALCUTATIONS Yesterday we stopped before calculating the amount of materials needed and remaining. 2 Gc + 1M + 3 Cp --> 1 Sm Given 4 graham crackers, 5 marshmallows and 9 chocolate pieces what is the theoretical yield of S'more 1 Sm 4 Gc x = 2 Sm 2 Gc 1 Sm 5 M x = 5 Sm 1 M 1 Sm 9 Cp x = 3 Sm 3 Cp Now let's finish the problem and solve for how much of the excess reactants are remaining. You have done this before in the S'more lab. 34

35 Let's do a limiting reactant problem from start to finish. Given: Mg (s) + HCl (aq) 4 MgCl2 (aq) + H2 (g) If 215 g of magnesium reacts with 15.2 moles of HCI, determine: The theoretical yield of H2 (in moles) The limiting reactant and the excess reactant The quantity of the excess reactant remaining (in grams) 35

36 LIMITING REACTANT PROBLEM HINTS (HINT: A limiting reactant problem will have two GIVENS) 1. Use the Hints for Simple Stoichiometry to calculate the mols of the UNKNOWN for both of the GIVENS using two separate T-charts. 2. Identify the following: a. The lesser of the two values calculated for step #1 is the THEORETICAL YIELD (TY). b. The reactant that gave the TY is the LIMITING REACTANT (LR). c. The other reactant is the EXCESS REACTANT (ER). 3. Calculate the amount of ER used by using Simple Stoichiometry and the TY as the GIVEN. You will have to determine if you want to solve for the amount of ER used in grams or moles depending on what the problem asks for, or based on the unit that it was originally given in the problem. 4. To calculate the amount of ER remaining, subtract the amount used up (as calculated in step #3) from the amount given in the problem. 36

37 EXCESS REACTANT CALCUIATIONS HOMEWORK 1. N2 (g) + H2 (g) NH3 (g) If you are given 115 moles of nitrogen and 109 moles of hydrogen determine: The theoretical yield of NH3 (in moles) The limiting reactant and the excess reactant The quantity of the excess reactant remaining (in moles) 37

38 2. Na (s) + Cl2 (g) NaCl (s) If you are given 184 grams of sodium and 210 grams of chlorine determine: The theoretical yield of NaC1 in grams The limiting reactant and the excess reactant The quantity of the excess reactant remaining in moles 38

39 3. NH3 (g) + O2 (g) NO2 (s) + H2O (l) If you are given 16.7 moles of NH3 and grams of oxygen determine: The theoretical yield of H2O in moles The limiting reactant and the excess reactant The quantity of the excess reactant remaining in grams 39

40 4. Write the complete balanced equation for: Solid copper (1) sulfide reacts with oxygen gas to produce solid copper (II) oxide and SO2 gas. If you are given grams of copper (I) sulfide and grams of oxygen determine: The theoretical yield of SO2 in grams The limiting reactant and the excess reactant The quantity of the excess reactant remaining in grams 40

41 Limiting Reagent Lab Purpose: The purpose of this lab is to: perform a double replacement reaction using given quantities of reactants determine which reactant is the limiting reactant calculate the theoretical yield of the solid precipitate compare the theoretical yield to the actual amount of precipitate formed. Background info: We will be able to collect the product by a separation technique known as filtration. We will combine the reactants, allowing them to react. Evidence of the reaction should be obvious, as a precipitate appears in the reaction vessel. The products will then be slowly poured through a funnel lined with a sheet of filter paper. This should collect the precipitate, but allow the rest of the aqueous materials to pass through. The liquid that passes through the filter paper should be collected to be sure that no solid particles are lost. This clear liquid that passes through the filter paper is called the filtrate. Distilled water should be used to wash the reaction vessel to get all the precipitate out and onto the filter paper. The filtrate should then be gently washed with distilled water to ensure no other aqueous compounds remain on the filter paper. The filter paper is then dried to complete the separation. Given the following reaction... Iron (III) Chloride + Sodium Hydroxide Sodium Chloride + Iron (III) Hydroxide 1. In the space provided above, write out the balanced reaction using the chemical formulas for all the compounds. 2. Add the physical state of each compound to the balanced equation using your solubility chart. 3. Underline the compound we will be able to collect at the end (the solid precipitate). Safety: Sodium Hydroxide can cause severe skin burns. At no time should you ever touch this chemical with your hands. Gloves should be worn when dispensing this chemical. Goggles MUST be worn at all times during the lab. Iron III Chloride is a skin and tissue irritant. Care should be taken not to touch this chemical. Dispose of your final product and filter paper directly into the garbage. Immediately wash any skin that comes into contact with any of the chemicals used in this experiment Wash your hands when you are finished 41

42 Procedure: Day 1 To make sure we finish by the end of class, partners will split up steps 1-4. Determine who is 1 and 2. Partner 1 Partner 2 Partner 1 does steps l-2, while Partner 2 does steps Take your clean dry beaker to the balance. Place the beaker on the balance and press tare. The beaker should weigh 0.00 g. Now add about 0.3 grams Iron (III) Chloride to the beaker. RECORD the exact amount used in your data table 2. Add about 25 ml of distilled water to the beaker and stir until it is completely dissolved. Partner 2 does steps 3-4 while Partner 1 does steps Take your second clean dry beaker to the balance. Place the beaker on the balance and press tare. The beaker should weigh 0.00 g. Now add about l.0 grams of Sodium Hydroxide to the beaker. RECORD the exact amount used in your data table. 4. Add about 25 ml of distilled water to the second beaker and stir with a different stir rod until it is completely dissolved. Partners now work together. 5. Slowly combine these two solutions by pouring one into the other, stirring with a stirring rod. 6. Write your name/class period IN PENCIL on a piece of filter paper. Measure the mass of the filter paper. RECORD the exact mass in your data table. 7. Clean an empty beaker and place it under your funnel set-up to collect the filtrate. Fold the filter paper, place in funnel and moisten with the DI water bottle. Make sure the end of the funnel is pressed against the side of the beaker so the water streams done the side (this goes faster than letting it drip - the polarity of the water helps us filter!!) 8. Pour the reacted solution through the filter paper / funnel assembly. Be sure to not pour above the level of the filter paper! You want the filtrate to be clear. 9. Wash the stirring rod and reaction beaker with distilled water. Then pour this into the filter paper as well. 10. Take out the filter paper with the precipitate on it. Place it on the tray to dry overnight. 11. Wash and dry all your materials. Dispose of gloves. Day 2; 12. Mass the precipitate and filter paper and RECORD the exact mass in your data table. 42

43 Data Table: Mass of iron (III) chloride used Mass of sodium hydroxide used Mass of dry filter paper with pencil marks Mass of dried filter paper with product Calculations: 1. Based on the mass of the reactants you used in this lab, use stoichiometry to determine the mass of precipitate we would expect to collect (i.e.: the TY). Also calculate the mass of the excess reactant remaining. 2. Label in question 1 above: a. theoretical yield of the precipitate in grams (TY) b. limiting reactant (LR) c. excess reactant (ER) d. excess reactant remaining (in grams) (ER-left over) 43

44 3. Using your data, determine the mass of Precipitate that you actually collected in the lab. SHOW YOUR WORK! (This is your actual yield). 4. Determine the % yield for this experiment. (% yield = [actual lab yield / theoretical calculated yield] x 100%) 5. Determine a way experimentally that you could verify the presence of your excess reactant in your filtrate. 6. Assuming you did not get 100.0% yield in this experiment, what could be possible sources of error? NOTE: YOU MAY CHECK YOUR ANSWERS TO ALL CALCULATION ON SHAREPOINT if your teacher has uploaded the "LR lab MAGIC CALCULATOR" 44

45 Chemistry Stoichiometry Stoichiometry Extra Practice Balance the following equations and answer the following questions: 1. Li3N (aq) + H2O (l) NH3 (aq) + LiOH (aq) a. What mass of H2O in grams is needed to react with 98.7 g of Li3N? b. How many moles of NH3 are produced from 5 moles of H2O? c. How many grams of LiOH are produced from 98.7 g of Li3N? 2. CO (g) + H2 (g) CH3OH a. How many grams of H2 are needed to react with 5.74 mol of CO? b. How many moles of CH3OH are produced from 5 moles of H2? 3. Na2O2 (aq) + H2O (l) O2 (g) + NaOH (aq) a. Calculate the mass of Na2O2 in grams needed to form 3.20 g of O2. b. How many grams of NaOH are produced when 3.2 g of O2 is formed? c. When 0.48 g of Na2O2 reacts with plenty of H2O, how many grams of O2 are formed? 45

46 4. Al(s) + O2 (g) Al2O3 (s) a. How many moles of Al are needed to form 2.3 moles of Al2O3? b. How many moles of O2 are required to react completely with 0.84 mol of Al? c. How many moles of Al2O3 form when 17.2 moles of O2 react? 5. CaC2 (s) + H2O (l) C2H2 (g) + Ca(OH)2 (s) a. How many grams of C2H2 are produced from g of CaC2? b. How many moles of CaC2 are needed to react with 98.0 g of H2O? c. How many grams of Ca(OH)2 are produced from 5.34 moles of C2H2? 46

47 LIMITING REACTANTS Show all your work on a separate sheet of paper!! (or the blank pages at the end of the packet) 1. A quantity of 96.0 mol of hydrochloric acid reacts with 28.3 mol of solid aluminum hydroxide. a. Determine the theoretical yield of aluminum chloride in grams. b. Also determine the limiting reactant, the excess reactant and moles of excess remaining. 2. A quantity of 5.37 mol of solid sodium reacts with 20.9 g of aqueous aluminum nitrate. a. Determine the theoretical yield of aluminum in grams. b. Then determine limiting reactant, excess reactant, and the grams of excess reactant remaining. 47

48 3. If g of aqueous calcium chloride reacts with g of aqueous lithium phosphate. a. Determine the theoretical yield of lithium chloride in grams. b. Then determine limiting reactant, excess reactant, and the grams of excess reactant remaining mol of aqueous ammonia (NH3) reacts with g of oxygen to produce nitrogen dioxide gas and water. a. Determine the theoretical yield of water in grams. b. Then determine the limiting reactant, excess reactant, and the grams of excess reactant remaining. 5. A quantity of g solid copper (I) sulfide reacts with 10.2 mol oxygen gas to produte solid copper (II) oxide and sulfur dioxide gas. a. Determine the theoretical yield: of sulfur dioxide in grams. b. Then determine the limiting reactant, excess reactant and the mass of excess reactant remaining. 48

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