Answer
Please see the work below.
Work Step by Step
Entropy change increases when a system changes from an ordered state to a disordered state.
Entropy change decreases when a system changes from a disordered state to an ordered state.
(a) 2KClO4(s) → 2KClO3(s) + O2(g)
In this reaction the conversion is from ordered solid state to disordered gaseous state, so entropy increases.
(b) H2O(g) → H2O(l)
In this reaction the conversion is from disordered gaseous state to ordered liquid state, so entropy decreases.
(c) 2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)
In this reaction the conversion is from ordered solid and liquid state to disordered liquid and gaseous state respectively, so entropy increases.
(d) N2(g) → 2N(g)
In this reaction the conversion is from ordered gaseous diatomic state to disordered monatomic gaseous state, so entropy increases.
