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Stoichiometry
June 2010
1. Balance the following chemical equations:
A. __C2H5OH(l) + __O2(g) → __C O2(g) + __H2O(g)
B. __C4H9OH(l) + __O2(g) → __C O2(g) + __H2O(g)
C. __C4H10(l) + __O2(g) → __C O2(g) + __H2O(g)
D. __C25H52(s) + __O2(g) → __C O2(g) + __H2O(g)
E. __Fe(s) + __O2(g) → __Fe2O3(s)
F. __SO2(g) + __HF(l) → __SF4(g) + __H2O(l)
G. __Fe2O3(s) + __Mg→__MgO(s) + __Fe(s)
H. __NH3(g) + __O2 → __NO(g) + __H2O(g)
I. __NaBH4(s) + __H2SO4(aq) → __B2H6(g) + __H2(g) + __Na2SO4(aq)
2. Consider the following balanced chemical equation:
2 C2H6(g) + 7 O2(g) → 4 CO2(g) + 6 H2O(g)
A. How many molecules of O2 are needed for the complete combustion of 3000 molecules of C2H6?
B. How many molecules of CO2 are produced from the complete reaction of 100 molecules of O2?
C. Can a chemical reaction produce a fraction of a molecule?
D. How many moles of O2 are needed for the complete combustion of 5.00 moles of C2H6?
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E. How many moles of CO2 are produced from the complete reaction of 15.00 moles of O2?
F. Can a chemical reaction produce a fraction of a mole?
G. How many grams of O2 are needed for the complete reaction of 3.00 moles of C2H6?
H. How many grams of CO2 are produced by the complete reaction of 10.00 moles of C2H6?
I. How many grams of O2 are needed for the complete reaction of 100.0 grams of C2H6?
J. How many grams of H2O are produced by the complete reaction of 100.0 grams of C2H6?
3. Consider the following balanced chemical equation:
CH4(g) + 4 Cl2(g) → CCl4(l) + 4 HCl(g)
A. Which reactant is limiting when 2.00 moles of CH4 and 7.00 moles of Cl2 are mixed and reacted?
B. Which reactant is limiting when 200.0 grams of CH4 and 700.0 grams of Cl2 are mixed and
reacted?
C. How much CCl4 is produced when 200.0 grams of CH4 and 700.0 grams of Cl2 are mixed and
reacted?
4. A 100.0 gram sample of a mixture of salt and water (NaCl/H2O) is heated until all the water is gone. The
remaining mass is 15.40 grams. What is the percent salt (NaCl) in the mixture?
5. A 20.00 gram sample of a mixture of BaCl2 and BaCl2 . 2H2O is heated until all the water is gone. The
remaining mass is 18.50 grams. What is the percent BaCl2 in the mixture?
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6. What is the percent composition of C2H6?
7. Calculate both the empirical formula and the molecular formula for a compound which is 80.0 % carbon
and 20.0 % hydrogen.
8. Calculate both the empirical formula and the molecular formula for a compound with the following
composition: C = 37.8%, H = 6.3%, and Cl = 55.9 %. The molecular weight is 127.
9. Calculate both the empirical formula and the molecular formula for a compound with the following
composition: C = 40.00%, H = 6.71%, and O = 53.29 %. The molecular weight is 180.
10. Calculate both the empirical formula and the molecular formula for an organic compound containing
only carbon, and hydrogen. A 1.000 g sample of this compound was combusted in air to give the
following results: 2.933 g of CO2 and 1.800 g of H2O. The molecular weight is 30.0 g/mole.
11. Calculate both the empirical formula and the molecular formula for an organic compound containing
only carbon, hydrogen, and oxygen. A 0.537 g sample of this compound was combusted in air to
given the following results: 1.030 g of CO2 and 0.632 g of H2O. The molecular weight is 230.
12. The elements A and Z combine to form two different compounds: A2Z3 and AZ2. If 0.15 mole of A2Z3
has a mass of 15.9 g and 0.15 mole of AZ2 has a mass of 9.3 g, what are the atomic masses of A and Z?