Question

For a phase change
$H _{2} O ( l ) \underset{0^{\circ} C , 1 \text{bar} }{\rightleftharpoons} H _{2} O ( s )$

• A. $\Delta G =0$
• B. $\Delta S =0$
• C. $\Delta H =0$
• D. $\Delta U =0$

Answer 1

Answer: (A)

$H _{2} O ( l ) \underset{0^{\circ} C , 1 \text{bar} }{\rightleftharpoons} H _{2} O ( s )$
for equilibrium at constant pressure and temperature.
$G = A + PV$
$d G = d A + PdV + VdP$
At constant $T$ and $P$ we obtain
$(\partial G )_{ T , P }=0$
for infinitesimal change
$(\Delta G )_{ T , P }>0$