Q26 / 155 · WBJEE 2016 · Chemistry

The condition for a reaction to occur spontaneously is

  • A
    $\Delta H$ must be negative
  • B
    $\Delta S$ must be negative
  • Correct answer
    C
    $(\Delta H-T \Delta S)$ must be negative
  • D
    $(\Delta H+T \Delta S)$ must be negative

Solution

For a spontaneous reaction, $\Delta G$ = negative and $\Delta S=$ positive $$ \Delta G=\Delta H-T \Delta S=-v e $$ Hence, $\Delta H-T \Delta S=-$ ve only when $\Delta S=+$ ve and $$ \Delta H=-v e $$

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

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