1. Molecular Composition of Gases
Stoichiometry of Gases

2. Objectives
Apply the principles of stoichiometry to determine the volume of any gas that is produced or consumed in a chemical reaction.

3. Volume-Volume Calculations
At STP, what volume of hydrogen gas is needed to react completely with 4.55 L of oxygen gas to produce water vapor?
2 H2 + O2  2 H2O

4. Stoichiometry of Gases
2 CO(g) + O2 (g)  2 CO2 (g)
2 molecules CO + 1 molecule O2  2 molecules CO2
2 mol CO + 1 mol O2  2 moles CO2
2 L CO + 1 L O2  2 L CO2

5. Volume-Volume Calculations
Xenon gas reacts with fluorine gas to produce the gaseous compound xenon hexafluoride. If a researcher needs 3.14 L of xenon hexafluoride for an experiment, what volumes of xenon and fluorine should be reacted. Assume all volumes are measured under the same conditions of temperature and pressure. Xe + 3 F2  XeF6

6. Volume-Volume Calculations
Nitric acid can be produced by the reaction of gaseous nitrogen dioxide with water.
3 NO2 (g) + H2O(l)  2 HNO3 (l) + NO(g)
If 708 L of NO2 gas react with water, what volume of NO gas will be produced? Assume the gases are measured under the same conditions.

7. Volume-Mass Calculations
Aluminum granules are a component of some drain cleaners because they react with sodium hydroxide to release both heat and gas bubbles, which help clear the drain clog. The reaction is… 2 NaOH(aq) + 2 Al(s) + 6 H2O(l)  2 NaAl(OH)4 (aq) + 3H2 (g) What mass of aluminum would be needed to produce 4.00 L of hydrogen gas at STP?

8. Volume-Mass Calculations
Air bags in cars are inflated by the sudden decomposition of sodium azide, NaN3, by the following reaction:
2 NaN3 (s)  3 N2 (g) + 2 Na(s)
What volume of N2 gas, measured at 1.30 atm and 87oC, would be produced by the reaction of 70.0 g of NaN3?

9. Volume-Mass Calculations
Rocket propulsion systems and some explosives employ reactions that suddenly produce a large volume of hot gas from a small volume of reactants. For example, the explosive substance, nitroglycerin undergoes the following decomposition reaction when detonated.
4 C3H5(ONO2)3 (l)  12 CO2 (g) + 10 H2O(g) + 6 N2 (g) + O2(g)
Calculate the total volume of gases produced by the reaction of 4 moles of nitroglycerin.
(12 mol + 10 mol + 6 mol + 1 mol)(22.4 L/mol) = 650. L