Question

On the basis of the following graph (P – V graph), choose the correct statements.

• A. The entropy change for the overall process is zero
• B. For the overall process $\Delta H>\Delta E$
• C. Total work done, W = q
• D. Total work = – 620.77 J

Answer 1

Answer: (A), (D)

The correct options are
A The entropy change for the overall process is zero
D Total work = – 620.77 J

The overall process can be depicted as

Thus it is a cyclic process.
Hence, $\Delta E=0,\Delta H=0,\Delta S=0$ (cyclic process) $1^{st}$ law
and $\Delta E$ = q + W
$\therefore$ 0 = q + W
or q =-W
Total work done = $W_{A\to B}+W_{B\to C}+W_{C\to A}$
$\therefore W=-P(V_B-V_A)+0+2.303nRTlog\frac{V_C}{C_A}Fromidealgaslaw,PV=RT=-(40-20)+0+2.303\times 20\times log\frac{V_C}{V_A}$
= – 6.13 litre-atmosphere
= – 620.77 J