In which of the following process entropy increases?
a) A liquid evaporates to vapour.
b) Temperature of a crystalline solid lowered from 115 K to 0 K.
c) `CaCO_(3(s))toCaO_((s))+CO_(2(g))`
d) `Cl_(2(g))to 2Cl_((g))`

Explanation

a) When a liquid evaporates to vapour randomness increases in the vapour state as `triangleS` is +ve, Hence the process is spontaneous.
b) If the temperature of the crystalline solid is lowered to OK it becomes perfectly ordered. No disorder is noticed, Hence such a process is not spontaneous.
c) `CaCO_(3(s)) to CaO_((s)) + CO_(2(g))`
`triangleS` is very slightly positive. If temp is increased `triangleS` becomes more positive.
(d) `Cl_(2(g)) to 2Cl_(g)`
It is an endothermic process there is no considerable increase in entropy. The process is not spontaneous