Stoichiometry Predicting amounts of reagents needed or amounts of products made

2 C 2 H O 2  4 CO H 2 O How much CO 2 will be produced if 4 moles of C 2 H 6 are consumed? Stoichiometry problems: 1) Start with balanced chemical equation 2) Problem will ask how many moles/liters given yield certain amount of something else

2 C 2 H 6 4 CO 2 2 C 2 H O 2  4 CO H 2 O CO 2 C 2 H 6 How much CO 2 will be produced if 4 moles of C 2 H 6 are consumed? 4 X ___________ 4 moles C 2 H 6 2 moles C 2 H 6 = X moles CO 2 4 moles CO 2 X = 8 moles CO 2

2 C 2 H 6 6 H 2 O 2 C 2 H O 2  4 CO H 2 O H 2 O C 2 H 6 How much H 2 O will be produced in the combustion of 5 moles of C 2 H 6 ? 5 X 5 moles C 2 H 6 ____________ 2 moles C 2 H 6 = X moles H 2 O ___________ 6 moles H 2 O X = 15 moles H 2 O

2 C 2 H 6 7 O 2 2 C 2 H O 2  4 CO H 2 O oxygen C 2 H 6 How much oxygen will react with 5 moles of C 2 H 6 ? 5 X 5 moles C 2 H 6 ___________ 2 moles C 2 H 6 = X moles O 2 ___________ 7 moles O 2 X = 17.5 moles O 2

Coefficients in Balanced Equations Give relative number of particles in rxn Give relative number of moles in rxn Coefficients: mole ratios of each component use these relationships in MOLE-MOLE problems to convert from moles of 1 substance to moles of another substance

Volume/Volume Word Problems Involving Gases

Gas-Phase Equations 1 mole any gas occupies same volume as any other gas (At STP = 22.4 L/mol) In reactions where ALL reactants & products are gases: coefficients represent ratio of volumes of gases

15 x N 2 (g) + 3 H 2 (g)  2 NH 3 (g) How much hydrogen gas will react with 15 liters of nitrogen gas? 15 L N 2 (g) _________ 1 L N 2 (g) = X L H 2 (g) _________ 3 L H 2 (g) X = 45 L H 2 (g)