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Assertion : A reaction which is spontaneous and accompanied by decrease of randomness must be exothermic.
Reason : All exothermic reactions are accompanied by decrease of randomness.
Options:
Reason : All exothermic reactions are accompanied by decrease of randomness.
Solution:
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Verified Answer
The correct answer is:
If assertion is true but reason is false.
$\Delta G=\Delta H-T \Delta S$
As the reaction is accompanied by decrease in randomness,
$\Delta G=\Delta H+T \Delta S \quad[\because \Delta S$ is negative $]$
For reaction to be spontaneous $\Delta G$ should be
negative which is possible only if reaction is highly exothermic i.e $\Delta H$ is negative. Exothermic reactions may be accompanied by increase or decrease of randomness.
As the reaction is accompanied by decrease in randomness,
$\Delta G=\Delta H+T \Delta S \quad[\because \Delta S$ is negative $]$
For reaction to be spontaneous $\Delta G$ should be
negative which is possible only if reaction is highly exothermic i.e $\Delta H$ is negative. Exothermic reactions may be accompanied by increase or decrease of randomness.
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