Name. Academic Chemistry Stoichiometry Notes. Unit #10 Test Date: cincochem.pbworks.com

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1 Name Academic Chemistry Stoichiometry Notes Unit #10 Test Date: cincochem.pbworks.com

2 Resources Unit 10 Common Polyatomic Ions List 20 Name Common Polyatomic Ion Ions Name Ion acetate C 2 H 3 O 2 or CH3 COO hypochlorite ClO ammonium + NH 4 nitrate NO 3 carbonate 2 CO 3 nitrite NO 2 chlorate ClO 3 perchlorate ClO 4 chlorite ClO 2 permanganate MnO 4 chromate 2 CrO 4 phosphate 3 PO 4 cyanide CN phosphite 3 PO 3 dichromate 2 Cr 2 O 7 silicate 2 SiO 3 hydrogen carbonate HCO 3 sulfate 2 SO 4 hydroxide OH sulfite 2 SO 3 1 = I 2 = II 3 = III 4 = IV 5 = V 6 = VI 2 cincochem.pbworks.com Stoichiometry

3 Unit 10 Intro to Stoichiometry What is stoichiometry? Stoich is the calculation of quantities in chemical reactions. We understand the LAW of Conservation of Mass, but WHAT does it mean when we look at chemical reactions? Before you begin, you need a chemical reaction. 2H 2 O 2H 2 + 1O 2 Conserved? (equal in reactants and products) Atoms = + Mass = + Moles = + Molecules = + and are ALWAYS conserved because of the law of conservation of matter (mass). and are NOT ALWAYS CONSERVED because they apply to each compound (coefficients), not each element. Stoichiometry cincochem.pbworks.com 3

4 Converting Moles to Moles Unit 10 How do I solve stoich problems? 1. All stoich questions require you to convert, so you will use dimensional analysis (railroad tracks). 2. You will need a chemical equation, so balance the equation, if necessary. 3. Write your railroad tracks and write the given, just like with moles. 4. You will be converting from one in the reaction to. So 5. You will use * to calculate. *Mole Ratios use the chemical equation to build ratios to between components of a reaction. They will be conversion factors in your work. Mole ratios for the decomposition of water: 2 H 2 O 2 H O 2 mole H 2 O mole H 2 O mole O 2 mole H 2 mole O 2 mole H 2 mole H 2 mole O 2 mole H 2 mole H 2 O mole H 2 O mole O 2 4 cincochem.pbworks.com Stoichiometry

5 Unit 10 Converting Moles to Moles Mole ratio conversions (basic stoich) 2 H 2 O 2 H O 2 1) How many moles of hydrogen gas are produced if 5.3 moles of water are decomposed? 2) How many moles of water are needed to form 1.7 moles of oxygen gas? Practice Using the below reaction, answer the following questions. 4 NH O 2 4 NO + 6 H 2 O 1) When 1.20 moles of ammonia (NH 3 ) are fixed with oxygen, how many moles of nitrogen monoxide (NO) are formed? 2) How many moles of oxygen gas are needed to react with 1.20 moles of ammonia? Stoichiometry cincochem.pbworks.com 5

6 Converting Mass to Mass Unit 10 Stoich with mass 1) It s a lot like solving mass conversions 2) Write the BALANCED equation. 3) Write the given (mass). 4) Convert to (using molar mass) 5) Convert to (using mole ratio) 6) Convert to (using molar mass) Example 1 H 2 O + 1 Na 2 O 2 NaOH Molar m. = Molar m. = Molar m. = a. Balance the equation b. Calculate the molar mass of each substance above. c. How many grams of NaOH are produced whem 12.5 grams of water are combined with sodium oxide (Na 2 O)? d. How many grams of Na 2 O are needed to react with 4.8 grams of water? 6 cincochem.pbworks.com Stoichiometry

7 Unit 10 Converting Mass to Mass Practice _1_ CaC 2 + _2_ H 2 O _1_ C 2 H 2 + _1_Ca(OH) 2 How many grams of Ca(OH) 2 are produced from 2.5 grams of water reacting with calcium carbide (CaC 2 )? How many grams of CaC 2 are needed to react with 9.3 grams of water? How many grams of C 2 H 2 are produced from 16.6 grams of CaC 2? Stoichiometry cincochem.pbworks.com 7

8 Molar Volume of a Gas Unit 10 Gases and moles The volume of a gas changes when or change. So, gas volume is measured with those factors removed, at STP, standard temperature and pressure. To find the of ANY gas at STP, we can use these ratios in our calculations: or Avogadro s Hypothesis -Avogadro theorized that equal VOLUMES of gases at STP contain the same number of. SINCE 1 mole = and 1 mol =, we can say that = Examples What is the volume, at STP, of mol CH 4 gas? At STP, how many moles are there in 67.2 L of SO 2 gas? 8 cincochem.pbworks.com Stoichiometry

9 Unit 10 Molar Volume of a Gas Examples, continued At STP, how many grams are there in L helium gas? Practice How many liters are in 3.70 grams of N 2 gas at STP? How many grams are in 0.44 liters of C 2 H 6 gas at STP? How many atoms are in 7.6 grams of Ar gas at STP? Stoichiometry cincochem.pbworks.com 9

10 Gas Stoichiometry Unit 10 Stoich with gases We can use stoichiometry to calculate gas in chemical reactions using the relationships between all gases at STP. Examples _1_ Sn + _2_ HF _1_ SnF 2 + _1_ H 2 1. How many liters of HF (a gas) are needed to produce 9.40 liters of hydrogen gas, H 2, at STP? _2_ NH 4 NO 3 _2_ N 2 + _4_ H 2 O + _1_ O 2 2. How many liters of N 2 are formed when 228 g NH 4 NO 3 is decomposed at STP? 1 Li 3 N + 3 H 2 O 1 NH LiOH 3. How many grams of Li 3 N are needed to produce 15.0 liters of NH 3 gas at STP? 10 cincochem.pbworks.com Stoichiometry

11 Unit 10 Mixed Stoichiometry Mixed stoichiometry From mass, particles, or volume, we can use mole ratios convert between any value of any component of any chemical reaction! Examples 4 Al + 3 O 2 2 Al 2 O 3 1. How many moles of aluminum oxide will be produced if 2.5 moles of aluminum are used? 2 KClO 3 2 KCl + 3 O 2 2. How many particles of oxygen gas will be produced if 5.45 grams of potassium chlorate, KClO 3, are used? 3. How many liters of oxygen gas will be produced if 7.2 x formula units of KClO 3 are used? Stoichiometry cincochem.pbworks.com 11

12 Mixed Stoichiometry Unit 10 Practice 1 Fe + 2 HCl 1 FeCl H 2 4. How many grams of iron (II) chloride are produced from 6.57 grams of iron? 5. How many liters of hydrogen gas are produced from 14 x atoms of iron? 12 cincochem.pbworks.com Stoichiometry

13 Unit 10 Limiting Reactant Limiting reactant The limiting reactant is the reactant completely in the reaction. Other remaining reactants are called. The reaction when the limiting reactant is consumed. The amount of formed is determined by the limiting reactant. How do I determine which reactant is limiting? 1) Using stoich, calculate the of (in grams) that can be formed given the mass of reactant available. 2) Repeat for each. (Usually two reactants!) 3) Whichever reactant yields the smallest mass of product (in grams) is. Examples 2 H O 2 2 H 2 O 1. If 100 grams of H 2 and 80 grams of O 2 are used to produce H 2 O, which is the limiting reactant? Stoichiometry cincochem.pbworks.com 13

14 Limiting Reactant Unit If 50 grams of H 2 and 100 grams of O 2 are used to produce H 2 O, which is the limiting reactant? _1_ BaO + _1_ H 2 SO 4 _1_ BaSO 4 + _1_ H 2 O 1. If 28 grams of BaO and 140 grams of H 2 SO 4 are used to produce BaSO 4, which is the limiting reactant? 2. If 230 grams of BaO and 98 grams of H 2 SO 4 are used to produce H 2 O, which is the limiting reactant? 14 cincochem.pbworks.com Stoichiometry

15 Unit 10 Percent Yield Percent yield In a reaction, the yield is the amount of product that during a real lab investigation. The yield is the amount of product that could theoretically be formed (the result of stoichiometric ). The percent yield is the of the actual yield to the theoretical yield. It measures the of the lab process. It is usually than 100% (due to equipment, contamination, lab errors, etc...) % yield = Examples _2_ Al + _3_ CuSO 4 _1_ Al 2 (SO 4 ) 3 + _3_ Cu If 4.65 grams of Cu are produced when 1.87 grams of Al reacts with excess CuSO 4, what is 1) the actual yield of Cu? 2) the theoretical yield of Cu? Stoichiometry cincochem.pbworks.com 15

16 Percent Yield Unit 10 3) the percent yield of Cu? A chemist began with 200 grams of CuSO 4. After collecting and drying the product, 61.9 grams of Cu was obtained. What is 4) the actual yield of Cu? 5) the theoretical yield of Cu? 6) the percent yield of Cu? 16 cincochem.pbworks.com Stoichiometry

17 Unit 10 Solubility Tables Stoichiometry cincochem.pbworks.com 17

18 Extra Credit Unit cincochem.pbworks.com Stoichiometry

19 Unit 10 Extra Credit Across 2. the reactant that produces the smallest amount of reactant is called 7. the maximum amount of product that could be formed, the result of stoich math 8. yield measures the efficiency of a lab process x particles of a substance 12. any leftover reactants in a reaction are called reactants 14. a compound contains only nonmetals Down 1. stated that all gases at STP contain equal numbers of particles 3. an compound contains a cation and anion 4. one mole of a gas at stp contains gas volumes, in stoich, are measured at 6. stoich requires a chemical reaction 9. mole are used to convert from one substance to another in stoich 10. molar is the mass of a mole of a substance 11. the amount of product that forms in a real reaction 13. with mass, always conserved in a reaction Stoichiometry cincochem.pbworks.com 19

20 Periodic Table Unit cincochem.pbworks.com Stoichiometry