A cylinder contains 28 moles of an ideal gas at a temperature of 300 K. The gas

Question

A cylinder contains 28 moles of an ideal gas at a temperature of 300 K. The gas is compressed at constant pressure until the final volume equals 0.7 times the initial volume. The molar heat capacity at constant volume of the gas is 24.0 J/mol · K and the ideal gas constant is R = 8.314 J/mol · K. The heat absorbed by the gas is closest to
A cylinder contains 28 moles of an ideal gas at a temperature of 300 K. The gas is compressed at constant pressure until the final volume equals 0.7 times the initial volume. The molar heat capacity at constant volume of the gas is 24.0 J/mol · K and the ideal gas constant is R = 8.314 J/mol · K. The heat absorbed by the gas is closest to

Part A

-60 kJ.
81 kJ.
60 kJ.
-21 kJ.
-81 kJ.

Explanation / Answer

Heat absorbed is given by:

Q = n*(Cv + R)*dT

At constant pressure

V2/V1 = T2/T1

T2 = (V2/V1)*T1

T2 = (0.7*V/V)*300 = 210 K

dT = 210 - 300 = -90

n = 28 moles

Cv = 24 J/mol-K

R = 8.314 J/mol-K

Using these values

Q = -28*(24 + 8.314)*90

Q = -81431 J

Q = -81 kJ

Correct option is E.

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