Name: ________________________
Hour: ____ Date: ___________
Chemistry: Review Problems for the Gas Laws
Do the following problems, showing your work and including all proper units.
Graham’s Law
1. At 350oC, nitrogen has a velocity of 800 m/s. Find the velocity of helium at the same temperature.
2. At room temperature, acetylene (C2H2) has a velocity of 480 m/s. At the same temperature, an unknown noble
gas has a velocity of 267 m/s. What is the unknown gas?
Gas Laws with One Term Constant
3. A sample of gas has an initial volume of 25 L and an initial pressure of 3.5 atm. If the pressure changes to 1.3
atm, find the new volume, assuming that the temperature remains constant.
4. A sample of neon is at 89oC and 123 kPa. If the pressure changes to 145 kPa and the volume remains
constant, find the new temperature, in oC.
Combined Gas Law
5. A gas at STP occupies 28 cm 3 of space. If the pressure changes to 3.8 atm and the temperature increases to
203oC, find the new volume.
6. A sample of sulfur dioxide (SO2) is initially at a temperature of 133oC, a volume of 20 L, and a pressure of 850
mm Hg. If the volume changes to 25 L and the temperature increases to 181 oC, find the new pressure.
Ideal Gas Law
7. 25 g of methane (CH4) has a pressure of 4.44 atm at 250oC. Find the volume occupied by the gas.
8. A sample of gas has a volume of 5.0 L when at a temperature of 310 K and a pressure of 220 kPa.
a)
Find the number of moles of gas.
b) If there are 56 g of the gas in the sample, which noble gas is it?
Manometers: For each manometer, find the pressure of the confined gas, in kPa.
9.
10.
atmospheric pressure
= 101.3 kPa
atmospheric pressure
= 100.4 kPa
Gas Stoichiometry
11. a) Write a balanced chemical equation for the combustion of methane to form carbon dioxide and water.
b) If the methane has a volume of 0.65 L when under 100 kPa of pressure and at a temperature of 305 K,
find the mass of oxygen that is needed to use up all of the methane.
Answers:
1.
2.
3.
4.
2117 m/s
mm ~ 84 g, Kr
67 L
154oC
5. 12.8 cm3
6. 760 mm Hg
7. 15.1 L
8a. 0.43 moles
8b.
9.
10.
11b.
mm ~ 130 g, Xe
154.6 kPa
77.1 kPa
1.64 g O2
KEY
Chemistry: Review Problems for the Gas Laws
Do the following problems, showing your work and including all proper units.
Graham’s Law
1. At 350oC, nitrogen has a velocity of 800 m/s. Find the velocity of helium at the same temperature.
m 2  28 amu
Nitrogen 
v 2  800 m/s
v1

v2
m  4 amu
Helium  1
v 1  ? m/s
m2
m1
v1

800 m/s
v1
 2.64
800 m/s
v 1  2117 m/s
28 amu
4 amu
2. At room temperature, acetylene (C2H2) has a velocity of 480 m/s. At the same temperature, an unknown noble
gas has a velocity of 267 m/s. What is the unknown gas?
m 2  26 amu
Acetylene 
v 2  480 m/s
v1

v2
1.80 2
m2
m1

m2
26 amu
m 2  84 amu
m  ? amu
Unknown  1
v 1  267 m/s
480 m/s

267 m/s
m2
26 amu
Krypton (Kr  83.80 amu)
Gas Laws with One Term Constant
3. A sample of gas has an initial volume of 25 L and an initial pressure of 3.5 atm. If the pressure changes
to 1.3 atm, find the new volume, assuming that the temperature remains constant.
P1V1  P2 V2
V1  25 L
V2  ? L
P1  3.5 atm
P2  1.3 atm
3.5 atm 25 L   1.3 atm V2 
V2  67.3 L
4. A sample of neon is at 89oC and 123 kPa. If the pressure changes to 145 kPa and the volume remains
constant, find the new temperature, in oC.
P1
P
 2
T1
T2
T1  89 C  273  362 K
T2  ? C
P1  123 kPa
P2  145 kPa
o
o
K - 273 
123 kPa 145 kPa

362 K
T2
T2  427 K
o
C
427 - 273 
o
T2  154 o C
C
KEY – page 2
Chemistry: Review Problems for the Gas Laws
Combined Gas Law
5. A gas at STP occupies 28 cm 3 of space. If the pressure changes to 3.8 atm and the temperature increases to
203oC, find the new volume.
P1V1
P V
 2 2
T1
T2
V1  28 cm3
V2  ? cm3
T1  273 K
T2  203 o C  273  476 K
P1  1 atm
P2  3.8 atm
1 atm28 cm3   3.8 atmV2 
273 K
476 K
V2  12.8 cm3
6. A sample of sulfur dioxide (SO2) is initially at a temperature of 133oC, a volume of 20 L, and a pressure of 850
mm Hg. If the volume changes to 25 L and the temperature increases to 181oC, find the new pressure.
P1V1
P V
 2 2
T1
T2
V1  20 L
V2  25 L
T1  133 o C  273  406 K
P1  850 mm Hg
850 mm Hg 20 L   P2 25 L 
T2  181o C  273  454 K
406 K
P2  ? mm Hg
454 K
P2  760 mm Hg
Ideal Gas Law
7. 25 g of methane (CH4) has a pressure of 4.44 atm at 250oC. Find the volume occupied by the gas.
 1 mol CH 4
n  25 g CH 4 
 16 g CH 4
P  4.44 atm
PV  nRT

  1.5625 mol CH 4

T  250 o C  273  523 K
V  ? L
 R  0.0821 atm  L/mol  K
V 
V
nRT
P
1.5625 mol CH 4 0.0821 atm  L/mol  K 523 K 
4.44 atm
V  15.1 L
KEY – page 3
Chemistry: Review Problems for the Gas Laws
8. A sample of gas has a volume of 5.0 L when at a temperature of 310 K and a pressure of 220 kPa.
a) Find the number of moles of gas.
PV  nRT
P  220 kPa
n 
T  310 K
V  5.0 L
 R  8.314 kPa  L/mol  K
n
PV
RT
220 kPa5.0 L 
8.314 kPa  L/mol  K 310 K 
n  0.43 mol
b) If there are 56 g of the gas in the sample, which noble gas is it?
Molar Mass (MM) 
Molar Mass 
g
mol
56 g
 MM  131.2 g/mol
0.43 mol
 Xenon (Xe  131.29 g/mol)
Manometers: For each manometer, find the pressure of the confined gas, in kPa.
9.
atmospheric pressure
= 101.3 kPa
10.
atmospheric pressure
= 100.4 kPa
600 mm
mmm
200 mm m
m
600 mm
- 200 mm
150 mm
mmm
m
 101.3 kPa 
  53.3 kPa
400 mm
 760 mm Hg 
325 mm
- 150 mm
 101.3
kPa 
m
  23.3 kPa
175 mm
 760 mm Hg 
PBig  Psmall  Pheight
PBig  Psmall  Pheight
PBig  101.3 kPa  53.3 kPa
100.4 kPa  Psmall  23.3 kPa
PBig  154.6 kPa
Psmall  77.1 kPa
KEY – page 4
Chemistry: Review Problems for the Gas Laws
Gas Stoichiometry
11. a) Write a balanced chemical equation for the combustion of methane to form carbon dioxide and water.
CH4(g) + 2 O2 (g)  CO2 (g) + 2 H2O (g)
b) If the methane has a volume of 0.65 L when under 100 kPa of pressure and at a temperature of 305 K,
find the mass of oxygen that is needed to use up all of the methane.
P1V1
P V
 2 2
T1
T2
V1  0.65 L
V2  ? L
T1  305 K
T2  273 K
P1  100 kPa
P2  101.3 kPa
100 kPa0.65 L   101.3 kPaV2 
305 K
273 K
V2  0.574 L CH 4 @ STP
Substitute volume of methane gas @STP and solve ideal stoichiometry problem.
CH4(g) + 2 O2 (g)  CO2 (g) + 2 H2O (g)
0.574 L
xg
 1mol CH 4  2 mol O2  32 g O2 


  1.64 g O2
x g O2  0.574 L
 22.4 L CH 4  1mol CH 4  1mol O2 
Answers:
1.
2.
3.
4.
2117 m/s
mm ~ 84 g, Kr
67 L
154oC
5. 12.8 cm3
6. 760 mm Hg
7. 15.1 L
8a. 0.43 moles
8b.
9.
10.
11b.
mm ~ 131 g, Xe
154.6 kPa
77.1 kPa
1.64 g O2