JEE MAIN - Chemistry (2016 - 9th April Morning Slot - No. 12)
A reaction at 1 bar is non-spontaneous at low temperature but becomes spontaneous
at high temperature. Identify the correct statement about the reaction among the
following :
Both $$\Delta $$H and $$\Delta $$S are negative.
Both $$\Delta $$H and $$\Delta $$S are positive.
$$\Delta $$H is positive while $$\Delta $$S is negative.
$$\Delta $$H is negative while $$\Delta $$S is positive.
Explanation
We know that $$\Delta$$G = $$\Delta$$H $$-$$ T$$\Delta$$S
At low temperature : $$\Delta$$G is positive (non-spontaneous process), so $$\Delta$$H is positive and $$\Delta$$S is positive (T$$\Delta$$S < $$\Delta$$H as T is low).
At high temperature : $$\Delta$$G is negative (spontaneous process), so $$\Delta$$H is positive and $$\Delta$$S is positive (T$$\Delta$$S > $$\Delta$$H as T is high).
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