Choose the reaction with negative `DeltaS` value

Options

A. `2NaHCO_(3(s)) rarr Na_(2)CO_(3(s)) + CO_(2(g)) + H_(2)O_((g))`
B. `Cl_(2(g)) rarr 2Cl_((g))`
C. `2SO_(2(g)) + O_(2(g)) rarr 2SO_(3(g))`
D. `2KClO_(3(s)) rarr 2KCl_((s)) + 3O_(2(g))`

Answer

C

Explanation

`Delta S` has negative value if `Delta n_(g)` =-ve i.e. number of gaseous moles decreasing during a reaction.
For (a), `Delta n_(g)= 2- 0=2`
For (b), `Delta n_(g)= 2-1= 1` For (c), `Delta n_(g)= 2- 3= -1` (`Delta S` negative)
For (d), `Delta n_(g)= 3- 0= 3`
For (e), `Delta n_(g)= 1- 0=1`