Q46 / 180 · AIIMS 2019 (26 May) · Chemistry

In isolated system, find the condition for spontaneous reaction.

  • A
    $\Delta U=0, \Delta S=0, \Delta G=0$
  • B
    $\Delta U < 0, \Delta S>0, \Delta G < 0$
  • Correct answer
    C
    $\Delta U=0, \Delta S>0, \Delta G < 0$
  • D
    $\Delta U < 0, \Delta S < 0, \Delta G < 0$

Solution

For an isolated system, $q=0, w=0$ $\begin{aligned} & \therefore \quad \Delta U=0 \\ & \Delta G=\Delta H-T \Delta S\end{aligned}$ For spontaneous reaction, $\Delta G=-v$ e. $\Delta H=0$ for an isolated system. Thus, $\Delta S>0$ for the reaction to be spontaneous.

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

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