alleryStart learning →What volume does 40.8 mol of methane occupy at 25 degrees C and 745 torr? Use R = 0.08206 L atm/mol K.
A1.02 x 10^2 L
B9.98 x 10^2 L
C1.02 x 10^4 L
D1.02 x 10^3 L
Answer & Solution
Correct answer: D. 1.02 x 10^3 L
1. Rearrange PV = nRT to give V = nRT / P.
2. Convert the temperature to kelvin: 25 + 273 = 298 K.
3. Convert the pressure to atmospheres using 1 atm = 760 torr: 745 / 760 = 0.980 atm.
4. Multiply moles by R: 40.8 x 0.08206 = 3.348 L atm per K.
5. Multiply by the temperature: 3.348 x 298 = 997.8 L atm.
6. Divide by the pressure: 997.8 / 0.980 = 1018 L.
7. Written in standard form that is 1.02 x 10^3 L, or about 1020 litres.
8. Leaving the pressure in torr instead of atmospheres would shrink the answer by a factor of 760, which is the trap in this calculation.
_Source: OpenStax Chemistry (CC BY 4.0), Ch 9 "Gases", section 9.2 Relating Pressure, Volume, Amount, and Temperature: The Ideal Gas Law_
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