Question

Assertion : For the change, $H_2O_{(l)} \to H_2O_{(s)}$, $\Delta H = \Delta U$.
Reason : No enthalpy change is involved in this process.

• A. If both assertion and reason are true and reason is the correct explanation of assertion
• B. If both assertion and reason are true but reason is not the correct explanation of assertion
• C. If assertion is true but reason is false
• D. If both assertion and reason are false

Answer 1

Answer: (C)

For the change, $H_2O_(l) \to H_2O_{(s)}$, there is negligible change in volume.
$\therefore P \Delta V = \Delta n_gRT \approx 0$
Now, substituting the above value in eqn
$\Delta H = \Delta U + \Delta n_gRT$
we get, $\Delta H = \Delta U$.