Can a reaction be both exothermic and nonspontaneous?


The spontaneity of a reaction is given by $\Delta G$

$\Delta G < 0$ = spontaneous reaction

$\Delta G > 0$ = nonspontaneous reaction

$\Delta G$ is quantitatively described by the formula

$$\Delta G = \Delta H - T \Delta S$$

$\Delta H$ is negative (exotermic reaction)

When $T \Delta S$ product is more negative (smaller) than $\Delta H$, we have $\Delta G > 0$ and the reaction is nonspontaneous

  • $\begingroup$ Is there an example of such a reaction though? $\endgroup$ – Safdar Jul 25 '20 at 14:16
  • $\begingroup$ No, i agree with what you say. However it would be better if you could add an example of such a situation. Also, this would be temperature dependant. You might want to add that/ $\endgroup$ – Safdar Jul 25 '20 at 14:20
  • $\begingroup$ exothermic non spontaneous not endo thermic $\endgroup$ – Safdar Jul 25 '20 at 14:25
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    $\begingroup$ You can add that to the answer (+1) $\endgroup$ – Safdar Jul 25 '20 at 14:36
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    $\begingroup$ You can think of any combustion reaction $\endgroup$ – Namburu Karthik Jul 25 '20 at 16:39

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