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Chapter 12 Stoichiometry Problems – Answer Key
1. When aluminum is mixed with iron (III) oxide, Fe2O3 to produce iron metal and
aluminum oxide, Al2O3 along with a large quantity of heat. What is the molar ratio you
use to determine the mol of Fe if mol Fe2O3 is known?
Ans. 2 mols Fe = 1 mol Fe2O3
2. C(s) + FeCr2O4(s)  FeCr2(s) + CO2(g)
What mole ratio would you use to convert from moles of FeCr2O4 to moles of FeCr2.
Ans. 1 mol FeCr2 = 1 mol FeCr2O4
3. If 5.50 mol Calcium Carbide (CaC2) reacts with an excess of water, how many moles of
acetylene (C2H2) will be produced?
CaC2(s) + H2O(l)  Ca(OH)2(aq) + C2H2(g)
Ans. 5.50 mol C2H2
4. 3NaHCO3(aq) + H3C6H5O7(aq)  3CO2(g) + 3H2O(l) + Na3C6H5O7(aq)
How many moles of carbon dioxide can be produced if one tablet containing 0.0119 mol
NaHCO3 is dissolved?
Ans. 0.0119 mol CO2
5. CaCO3(s) + HCl(aq)  CaCl2(aq) + H2O(l) + CO2(g)
How many mol CaCO3 can be dissolved in 0.0250 mol HCl?
Ans. 0.0125 mol CaCO3
6. CH4(g) + Cl2(g)  CHCl3(g) + HCl(g)
How many grams of CH4 is needed to produce 50.0g CHCl3
Ans. 6.72g CH4
7. C2H5OH(l) + O2(g)  CO2(g) + H2O(g)
Determine the mass of CO2 produced from the combustion of 100.0 g C2H5OH
Ans. 191.0 g CO2
8. Calcium Carbonate, CaCO3 reacts with Carbonic Acid, H2CO3 to produce Calcium
Bicarbonate, Ca(HCO3)2. What mass of CaCO3 is produced when 3.05 g of Ca(HCO3)2is
used?
Ans. 1.88 g CaCO3
9. 4Au(s) + 8NaCN(aq) + O2(g) + 2H2O(l)  4NaAu(CN)2(aq) + 4NaOH(aq)
a. Determine the mass of gold that can be extracted if 25.0 grams of NaCN is used?
Ans. 50.2g Au
b. If the mass of the ore from which the gold was extracted is 16.8g. What is the
percent yield?
Ans. 33.5%
10. AgBr(s) + 2Na2S2O3(aq)  Na3Ag(S2O3)2 (aq) + NaBr(aq)
Determine the mass of Na3Ag(S2O3)2 produced if 0.275 g AgBr is removed.
Ans. 0.587g Na3Ag(S2O3)2
11. C12H22O11(aq) + 3O2(g)  2 H3C6H5O7(aq) + 3 H2O(l)
Determine the mass of citric acid, H3C6H5O7 produced when 2.50 mol C12H22O11 is used.
Ans. 961g H3C6H5O7
12. C2H5OH(l) + C3H7COOH(l)  C3H7COOC2H5(l) + H2O(l)
Determine the mass of ethyl butanoate, C3H7COOC2H5 produced if 4.50mol ethanol,
C2H5OH is used.
Ans. 523g C3H7COOC2H5
13. C12H22O11 + H2O  4C2H5OH + 4CO2
a. Determine the theoretical yield of ethanol in grams, C2H5OH if 684 g of sucrose,
C12H22O11 is used.
Ans. 369g C2H5OH
b. Calculate the percent yield if 349g of ethanol was obtained.
Ans. 94.6%
14. PbS + O2  PbO + SO2
a. Balance the equation and determine the theoretical yield of PbO in grams if
200.0g PbS is heated.
Ans. 186.6 g PbO
b. What is the percent yield if 170.0g PbO is obtained?
Ans. 91.10%
15. MnO2 + HCl  MnCl2 + Cl2 + H2O
a. Balance the equation and determine the theoretical yield of chlorine in grams if
50.0g of HCl react.
Ans. 24.3g Cl2
b. What is the percent yield of chlorine when 20.0g of Cl2 is found?
Ans. 82.3%