1. 14.5 NOTES Stoichiometry

2. II. Stoichiometric Calculations
A. Mass-mass calculations
Example: What mass of hydrogen gas can be formed when grams of zinc reacts with excess hydrochloric acid?
How to approach a stoichiometry problem:
1. Read the problem, then write a balanced equation.
2. Identify the given and desired quantities.
3. Determine molar masses if necessary.
4. Carry out the factor-label calculation, labeling the answer with units

3. a. Do the above example:
Zn + 2HCl  ZnCl2 + H2
Given: 12.5 grams of Zn (65.4g/mol) Find: mass of H2 (2.02g/mol)
12.5gZn x 1 mol Zn x 1 mol H2 x g H2
65.4 g Zn mol Zn mol H2 = g H2

4. b. When 10.0 grams of propane (C3H8) is burned in air, what is the mass of water formed?
C3H8 + 5O2  3CO2 + 4H2O
Given: 10.0g C3H8 *44.1g/mol) Find: mass of H2O (18.0g/mol)
10.0gC3H8 x 1 mol C3H8 x 4 mol H2O x g H2O
44.1 g C3H mol C3H mol H2O = 16.3g H2O