A sample of nitrogen, N2, occupies 45.0 mL at 27 °C and 600 torr. What pressure will it
have if cooled to –73 °C while the volume remains constant?
Volume is constant here
P1 = 600 torr = 0.7894 atm
T1 = 27 ℃ = 300 K
T2 = -73 ℃ = 200 K
P2 = ?
𝑃1
𝑃2
= 𝑇2
𝑇1
𝑃1
P2 = 𝑇1x T2 =
0.7894 𝑎𝑡𝑚
300 𝐾
x 200 K = 0.526 atm
A sample of carbon dioxide, CO2, occupies 0.300 L at 10 °C and 750 torr. What volume
will the gas have at 30 °C and 750 torr?
V1 = 0.300 L
T1 = 10 ℃ = 283 K
T2 = 30 ℃ = 303 K
V2 = ?
𝑉1
𝑇1
𝑉2
= 𝑇2
𝑉1
V2 = 𝑇1x T2 =
0.300 𝐿
283 𝐾
x 303 K = 0.3212 L
What is the volume of a sample of ethane at 467 K and 1.1 atm if it occupies 405 mL at 298
K and 1.1 atm?
V1 = 405 mL
T1 = 467 K
T2 = 298 K
V2 = ?
𝑉1
𝑇1
𝑉2
= 𝑇2
𝑉1
V2 = 𝑇1x T2 =
404 𝑚𝐿
467 𝐾
x 298 K = 258 mL
Methane, CH4, is being considered for use as an alternative automotive fuel to replace
gasoline. One gallon of gasoline could be replaced by 655 g of CH4. What is the volume of
this much methane at 25 °C and 745 torr?
Mass = 655 g
Temperature = 25 ℃ = 298 K
Pressure = 745 torr = 0.980 atm
V =?
V=
𝑚𝑅𝑇
𝑀𝑃
=
655 𝑔 𝑥 0.0821 𝑥 298
16 𝑥 0.980
= 1022 L
A sample of ammonia is found to occupy 0.250 L under laboratory conditions of 27 °C and
0.850 atm. Find the volume of this sample at 0 °C and 1.00 atm.
V1 = 0.250 L
T1 = 27 ℃= 300K
P1 = 0.850 atm
T2 = 0 ℃ = 273 K
P2 = 1 atm
V2 = ?
𝑃1𝑉1
𝑇1
V2 =
=
𝑃2𝑉2
𝑇2
𝑃1𝑉1𝑇2
𝑇1𝑃2
=
0.850 𝑎𝑡𝑚 𝑥 0.250 𝐿 𝑥 273 𝐾
300 𝐾 𝑋 1 𝑎𝑡𝑚
= 0.193 L
A gas was found to have a density of 0.0847 g/L at 17.0 °C and a pressure of 760 torr. What
is its molar mass? What is the gas?
d = 0.0847 g/L
T = 17 ℃ = 290K
P = 760 torr = 1 atm
Molar mass = ?
M=
𝑑𝑅𝑇
𝑃
=
0.0874 𝑋 0,0821 𝑋 290
1 𝑎𝑡𝑚
= 2.08 g/mol
A sample of chloroform gas weighing 0.494 g is collected in a flask with a volume of 129
cm3 at 99.6 °C when the atmospheric pressure is 742.1 mm Hg. What is the approximate
molar mass of chloroform?
Mass = 0.494 g
V = 129 mL = 0.129 L
T= 99.6 = 372.6 K
P = 742.1 mm Hg = 0.976 atm
M=
𝑚𝑅𝑇
𝑃𝑉
=
0.494 𝑋 0.0821 𝑋 372.6
0.129 𝑋 0.976
= 120 g/mol
A 5.73-L flask at 25 °C contains 0.0388 mol of N2, 0.147 mol of CO, and 0.0803 mol of H2.
What is the total pressure in the flask in atmospheres?
V = 5.73 L
T = 298 K
n = 0.0388 + 0.147 + 0.0803 = 0.2661
P=
𝑛𝑅𝑇
𝑉
=
0.2661 𝑋 0.0821 𝑋 298
5.73
= 1.14 atm
What is the pressure of a mixture of 0.200 g of H2, 1.00 g of N2, and 0.820 g of Ar in a
container with a volume of 2.00 L at 20 °C?
Moles of hydrogen = 0.200/2.008 = 0.0996 moles
Moles of nitrogen = 1/28 = 0.357
Moles of argon = 0.820/ 39.9 = 0.021
Total moles = 0.478
P=
𝑛𝑅𝑇
𝑉
=
0.478 𝑋 0.0821 𝑋 293
2
= 5.74 atm