Question

A gas undergoes change from state $A$ to state $B$ . In this process, the heat absorbed and work done by the gas is $5J\text{and}8J$ , respectively. Now gas is brought back to $A$ by another process during which $3J$ of heat is evolved. In this reverse process of $BtoA$ .

• A. $6J$ of the work will be done by the gas
• B. $6J$ of the work will be done by the surroundings on gas
• C. $10J$ of the work will be done by the surroundings on gas
• D. $10J$ of the work will be done by the gas

Answer 1

Answer: (B)

$forAtoB \\ q=5 \\ W= \, -8J, \\ ΔU_{AB}=dq+dw=5-8 \\ ΔU_{AB}=-3$

$forBtoA \\ ΔU_{BA}=dq+dw \\ ΔU_{BA}= \, +3 \\ 3=-3+W_{BA} \\ W_{BA}=6J$