Question

Temperature of 5 moles of a gas is decreased by 2K at constant pressure. Indicate the correct statement.

• A. Work done by the gas = 5R
• B. Work done by the gas = 10R
• C. Work done over the gas = 10R
• D. Work done = 0

Answer 1

The correct option is C

Work done over the gas = 10R

For 5 moles of gas at T, $P{V}_1=5RT$
For 5 moles of gas at $T-2,P{V}_2=5R(T-2)$
Hence, $P{V}_2-P{V}_1=P(V_2-V_1)=P\Delta V$
$=5R[T-2-T]=-10R$
Or, $-P\Delta V=10R(\Delta$ is negative, W is + i ve)