Verified Solution • 2025–26 Session moderate

QJEEM17Ch9a7d: JEE Main 2017 Chemistry - Class 11 JEEM17Ch9a7d Solution: A gas undergoes change from state A to state B. In this…

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

Multiple Choice Options

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

Step-by-Step Verified Solution

From first law of thermodynamics, we have

$\Delta$ U = q + w

$\bullet$ For state A to B : q = +5 J, w = $-$ 8 J and

$\Delta$ U_AB = 5 + ( $-$ 8) = $-$ 3 J

$\bullet$ For state B to A : q = $-$ 3 J

Since the internal energy is a state function, we have $\Delta$ U_BA = $-$ $\Delta$ U_AB. Therefore,

$\Delta$ U_BA = q + w

3 = $-$ 3 + w $\Rightarrow$ w = 6 J

Positive value of work indicates that 6 J of work is done by the surrounding on gas.

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