Question

The graph below represents the pressure and volume for a gas undergoing a cyclic process. Assume that Y and Z are on the same horizontal line, and Z and X are on the same vertical line.
Which table best expresses what happens as the gas goes through process $Z-X$ if $25J$ of heat is absorbed by the gas during the process?

• A. Internal Energy of Gas - Work Done by Gas, increases by $12.5J$ - is $12.5J$
• B. Internal Energy of Gas - Work Done by Gas, does not change - is $0J$
• C. Internal Energy of Gas - Work Done by Gas, does not charge - is $25J$
• D. Internal Energy of Gas - Work Done by Gas, increases by $25J$ - is $0J$
• E. Internal Energy of Gas - Work Done by Gas, decreases by $25J$ - is $50J$

Answer 1

Answer: (D)

Internal Energy of Gas - Work Done by Gas, increases by $25J$ - is $0J$

Given : $Q=+25$ $J$

Change in the volume of the gas during $Z\to X$ is zero i.e $V=0$

Thus work done by the gas during $Z\to X$, $W=0$ $J$

Using 1st law : $Q=\Delta U+W$

$\therefore$ $25=\Delta U+0$ $⟹\Delta U=25$ $J$