Chemistry - Thermodynamics - I Question with Solution | TestHub

Use the relation $\Delta H=\Delta U+\Delta n_{g}RT$, where $\Delta n_g$ is the change in gaseous moles.

For $A(g)\to A(l)$, the change is $\Delta n_g=0-1=-1$, which simplifies the formula to $\Delta H=\Delta U-RT$.

Substitute the given value $\Delta H=-3RT$ into the equation to get $-3RT=\Delta U-RT$, solving for $\Delta U=-2RT$.

Compare their absolute magnitudes: $|\Delta H|=3RT$ and $|\Delta U|=2RT$.

Since $3RT>2RT$, it proves that $|\Delta H|>|\Delta U|$, making (A) the correct choice.