Name ____________________________________________ Date _______________________ Period _______
Gas Stoichiometry and Molar Mass of a Gas
Solve the following problems on a separate sheet of paper. Show ALL work including equations and units. Round all
answers to the correct number of significant figures.
1. A 1.007 gram sample of an unknown gas exerts a pressure of 715 mm Hg in a 452 mL container at 23oC. What is
the molar mass of the gas?
2. Calculate the volume of hydrogen gas that can be produced by the reaction of 25.0 grams of zinc with an excess
of sulfuric acid at 25oC and 766 mm Hg.
3. Consider the following reaction:
4Al(s) + 3O2(g)  2Al2O3(s)
It takes 2.00 L of pure oxygen gas at STP to react completely with a certain sample of aluminum. What is the
mass of aluminum reacted?
4. Airbags are activated when a severe impact causes a steel ball to compress a spring and electrically ignite a
detonator cap. This causes sodium azide (NaN3) to decompose explosively according to the following reaction:
2NaN3(s)  2Na(s) + 3N2(g)
What mass of sodium azide must be reacted to inflate an air bag to 70.0 L of nitrogen gas at STP?
5. Uranium hexafluoride is a solid at room temperature, but it boils at 56oC. Determine the density of uranium
hexafluoride at 60oC and 745 torr.
6. Consider the reaction between 50.0 L of liquid methanol, CH3OH (density = 0.850 g/mL), and 22.8 L of O2(g) at
27oC and a pressure of 2.00 atm. The products of the reaction are CO2(g) and H2O(g). Calculate the number of
moles of H2O formed if the reaction goes to completion.
7. A 15.0 liter rigid container was charged with 0.500 atm of krypton gas and 1.50 atm of chlorine gas at 350oC.
The krypton and chlorine react to form krypton tetrachloride. What mass of krypton tetrachloride can be
produced assuming 100% yield?
8. Forty miles above Earth’s surface, the temperature is 250. K and the pressure is only 0.20 mm Hg. What is the
density of air, in g/L, at this altitude? Assume the molar mass of air if 28.96 g/mol.
9. You are asked to design an air bag for a car. You know that the bag should be filled with gas with a pressure
higher than atmospheric pressure, say 829 mm Hg, at a temperature of 22oC. The bag has a volume of 45.5 L.
What quantity, in grams, of sodium azide (NaN3) should be used to generate the required quantity of nitrogen
gas?
The gas-producing reaction is: 2NaN3(s)  2Na(s) + 3N2(g)
10. Calculate the density of CO2 at STP. Is CO2 more or less dense than air (density = 1.29 g/L at STP)?
11. Gaseous ammonia (NH3) is synthesized by the reaction
N2(g) + 3H2(g)  2NH3(g)
a. Assume that 355 L of H2 gas at 25oC and 542 mm Hg is combined with excess N2 gas. What amount of
NH3 gas, in moles, can be produced?
b. If this amount of NH3 gas is stored in a 125 liter tank at 25oC, what is the pressure of the gas?
12. Diborane reacts with O2 to give boric oxide and water vapor.
B2H6(g) + 3O2(g)  B2O3(s) + 3H2O(g)
a. What mass of O2 gas is required to react completely with 1.5 L of B2H6 at 25oC and 0.15 atm?
b. If you mix 1.5 L of B2H6 with 4.0 L of O2, each at 0oC and a pressure of 1.0 atm, what amount, in grams, of
water is produced?
13. If 25.0 L of nitrogen gas at 55oC and 782 mmHg are reacted with 49.9 L of hydrogen gas at 25oC and 884 mm Hg,
how many liters of ammonia, NH3, gas can be produced at 32oC and 765 mm Hg?
14. An unknown diatomic gas has a density of 3.164 g/L at STP. What is the identity of the gas?
15. Hydrazine, N2H4 , reacts with O2 according to the following equation:
N2H4(g) + O2(g)  N2(g) + 2H2O(l)
Assume the O2 needed for the reaction is in a 450 liter tank at 23oC. What must the oxygen pressure be in the
tank to have enough oxygen to consume 10.0 kg of hydrazine completely?