Question

The plots which does not represent isothermal expansion of an ideal gas is:

• A. A
• B. B
• C. C
• D. D

Answer 1

Answer: (B), (D)

D

For an isothermal expansion,
$P{V}_m=kso,P=k/V_m$
Where $k$ is a constant.

graph A :
So, here it means $P$ is directly proportional to $1/V_m$ i.e
$P\propto \frac{1}{V_m}$, so graph A is correct.

graph B:
Since, $P\propto \frac{1}{V_m}$ so graph of $Pvs{V}_m$ should be parabolic in nature but it is given as a straight line so it is not correct.

graph C:
For isothermal expansion,
$P{V}_m=$ constant
graph C is also correct.

graph D:
As $U$ is constant for an isothermal ideal gas expansion, hence graph D is incorrect.

So, incorrect graphs are B and D.

The correct graphs for B and D are given below.