Question

A reaction is non-spontaneous at the freezing point of water but is spontaneous at the boiling point of water then :

	$\Delta H$	$\Delta S$
(a)	+ ve	+ ve
(b)	- ve	- ve
(c)	- ve	+ ve
(d)	+ ve	-ve

• A. a
• B. b
• C. c
• D. d

Answer 1

Answer: (A)

For spontaneity $\Delta G=-$ ve

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

$\Delta H,$ for endothermic process $+$ ve

At lower temperature, $\Delta S+$ ve hence $\Delta G=+$ ve

But at high temperature $T \Delta S$ will be greater than

$\Delta H,$ hence $\Delta G=-$ ve, spontaneous