CHEM 219 HW 7 Stoichiometry Key (Questions and Verified Answers) Latest Update

HW 7 Stoichiometry Name______________________________________


1. One way to produce hydrogen gas is by reacting zinc with hydrochloric acid
according to the following reaction. How many grams of H2 can be produced with
10.0 g of Zn, MW (g/mol) Zn = 65.38, H2 = 2.02.

Zn + 2 HCl  ZnCl2 + H2
1 mole Zn 1 mol H 2 2.02 g H 2
# g H2 = ( 10.0 g Zn ) x x x = 0.309 g
65.38 g Zn 1 mole Zn 1 mole H 2




2. CaCO3 can be used to neutralization of excess stomach acid according to the
following reaction. For each gram (1.00 g) of CaCO3, how many grams of HCl can
be eliminated? MW: CaCO3 =100.1 g/mol, HCl = 36.46 g/mol.

CaCO3 + 2 HCl  CaCl2 + H2O + CO2
1mole CaCO 3 2 mol HCl 36.46 HCl
# g HCl = ( 1.00 g CaCO 3 ) x x x
100.1 g CaCO 3 1 mole CaCO 3 1 mole HCl

= 0.728 g




3. For a given reaction, the theoretical yield of a product is 72.6 g, and the actual
yield is 69.3 g. What is the percent yield of the reaction?

69.3 g
% yield = x 100 % = 95.5%
72.6 g




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