Question

Two moles of Helium gas are taken over the cycle ABCDA as shown in the P-T diagram. Assuming the gas to be ideal the work done on the gas in taking it from $D$ to $A$ is :

• A. $-414$ $R$
• B. $+414$ $R$
• C. $-690$ $R$
• D. $+690$ $R$

Answer 1

Answer: (A)

$-414$ $R$

Work done in D to A =$W_{DA}=nRT\ln \frac{P_i}{P_f}=2\times R\times 300\ln \frac{1}{2}$
$=-414R$