Q39 / 180 · AIIMS 2006 · Chemistry

For a phase change $\mathrm{H}_2 \mathrm{O}$ (l) (s)

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

Solution

$\Delta G^{\circ}=-R T \ln K$ [ $\Delta G^{\circ}=$ standard free energy change, $K=$ equilibrium constant] If a substance is in equilibrium between two phases at constant temperature and pressure, its chemical potential must have the same value in both the phases. $$ \therefore \Delta G^{\circ}=0 \text {. } $$

Hence, the correct answer is option: 'A'.

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