Gases WS 6
Gas Laws Review Sheet
Solving hints:
Standard P = 1 atm = 101.3 kPa = 760. mm Hg = 760. Torr
For what variable am I solving? (=unknown)
For what variables do I have values? (= known)
Which gas law is it?
What is the equation?
Rearrange equation, fill in the values and calculate
P1V1 = P2V2
@STP: 1 mol any gas = 22.4 L
T1
T2
R = 8.31kPaL = 0.0821 atmL = 62.4 mm HgL
PV = nRT
molK
molK
molK
1. A given mass of air has a volume of 6.0 L at 1 atm. What volume will it occupy at 190 mm Hg if the
temperature does not change? (24 L)
2. If 5.0 L of air at -50.0°C are warmed to 100°C. What is the new volume if the pressure remains constant?
(8.4 L)
3. The pressure in a car tire is 2.0 atm at 27°C. At the end of a long ride on a hot day the pressure has risen to
2.2 atm. What is the temperature of the air in the tire (volume constant)? (57oC)
4. Calculate the volume in liters at 204.1kPa if its volume at 524 mmHg is 2.4 L. (0.82 L)
5. A gas occupies 2.0 m 3 at 100. K, and exerts a pressure of 100. kPa. What volume would the gas occupy at
400. K if the pressure is increased to 200. kPa? (4.0 m 3)
6. A sample of methane that initially occupies 850. mL at 500. Pa and 500. K is compressed to a volume of
700. mL. To what temperature will the gas need to be cooled to lower the pressure of the gas to 200. Pa?
(165 K)
7. A sample of carbon dioxide occupies 45 m3 at 750 K and 500. kPa. What is the volume of the gas at STP?
(81 m3)
8. The mole fraction of nitrogen in air is 0.7808. Calculate the partial pressure of N 2 in air when the
atmospheric pressure is 760. torr. (593 Torr)
9. A weather balloon contains 1.10 x 105 mol of He and has a volume of 2.70 x 106 L at 1.00 atm. Calculate the
temperature of the He in the balloon in K and °C. (299 K, 26°C)
10. Suppose we have a 0.240 mol sample of ammonia gas at 25°C with a volume of 3.5L at a pressure of 1.68
atm. The gas is compressed to a volume of 1.35 L at 25°C. Use the ideal gas law to calculate the final
pressure. (4.35 atm)
11. Derive the universal gas constant, R, in pressure units of mmHg. (62.4 mmHg • L / mol • K)
12. Calculate the volume of 1.00 mol of CO2 at STP.
Gases WS 6
Solving Stoichiometry + Gas Law problems:
Standard P = 1 atm = 101.3 kPa = 760. mm Hg = 760. Torr
Write and balance equation (if necessary)
Get to moles of given
Use mole ratio to switch to other compound
Get required units
P1V1 = P2V2
@STP: 1 mol any gas = 22.4 L
T1
T2
R = 8.31kPaL = 0.0821 atmL = 62.4 mm HgL
PV = nRT
molK
molK
molK
13. Average lung capacity for humans is about 4.0 L. At 37°C (body temp) and 110 kPa, how many moles of
oxygen gas could your body hold? (0.17 mol)
14. At what temperature will 7.0 mol of helium gas exert a pressure of 1.2 atm in a 25.0 m 3 tank? (52,000 K)
15. How many L of hydrogen gas will be produced at 280. K and 96.0 kPa if 40.0 g of sodium react with excess
hydrochloric acid? (21.1 L)
16. A gas is compressed at constant temperature from from 27 L to 3.0 L. If the initial pressure of the gas is 0.50
atm, what is the final pressure? (4.5 atm)
17. A gas with a volume of 3.00 x 102 mL at 150.0°C is heated until its volume is 6.00 x 102 mL. What is the new
temperature of the gas if the P is unaltered? (846 K)
18. (Honors only) An unknown gas effuses through an opening at a rate 5.46 times faster than carbon dioxide
gas. What is the molecular mass of the unknown gas? (1.48 g/mol)
19. Mixtures of He and O2 are used in the “air” tanks of scuba divers. For a particular dive, 46 L of O 2 at 25°C
and 1.0 atm and 12 L of He at 25°C and 1.0 atm were both pumped into a 5.0 L tank. Calculate the partial
pressure of each gas and the total pressure in the tank at 25°C.(PO2 = 9.3 atm, PHe=2.4 atm, Ptotal=11.7 atm)
20. A 2.0L flask contains a mixture of nitrogen gas and oxygen gas at 25°C. The total pressure of the gaseous
mixture is 0.91 atm, and the mixture is known to contain 0.050 mol of N2. Calculate the partial pressure of
oxygen and the moles of oxygen present. (0.024 mol O2, 0.29 atm)
21. At a deep sea station 200. m below the surface of the Pacific Ocean, workers live in a highly pressurized
environment. How many liters of gas at STP on the surface must be compressed to fill the underwater
environment with 2.00 x 107 L of gas at 20.0 atm? Assume T remains constant. (question is not as hard as it
appears at first glance) (4.00 x 108 L)
22. Divers know that the pressure exerted by the water increases with depth. The pressure increases about 100.
kPa every 10.2 m. Given that the volume of a balloon is 4.0 L at STP, what is the volume 50. m below the
water’s surface at the same T? (0.69 L) (hint: two steps, takes some thinking)
23. How many liters of hydrogen at 35°C and 745 mm Hg are needed to react completely with 875 g of tungsten
oxide? (292 L)
WO3(s) + 3H2(g)  W (s) + 3H2O(l)
24. Magnesium will “burn” in carbon dioxide to produce elemental carbon and magnesium oxide. What mass of
magnesium will react with a 250 mL container of CO2 at 77°C and 65 kPa? (0.27 g Mg)