Predict which of the following reaction (s) has a positive entropy change?

(P) ${\mathrm{Ag}}^{+}\left(aq\right)+{\mathrm{Cl}}^{-}\left(aq\right)⟶\mathrm{AgCl}\left(s\right)$

(Q) ${\mathrm{NH}}_4\mathrm{Cl}\left(s\right)⟶{\mathrm{NH}}_3\left(g\right)+\mathrm{HCl}\left(g\right)$

(R) $2{\mathrm{NH}}_3\left(g\right)⟶{\mathrm{N}}_2\left(g\right)+3{\mathrm{H}}_2\left(g\right)$

It is known that,

${\mathrm{\Delta S}}_{\text{reaction }}^0={\mathrm{\Sigma \Delta S}}^0\mathrm{P}\text{ roduct }-{\mathrm{\Sigma \Delta S}}^0\text{ Reactant }$

On comparing it with standard molar entropies for substance, we get,

Gas Standard molar entropy > Liquids standard molar entropy

Liquid's standard molar entropy > Solids standard molar entropy.

Thus, reaction given in Q and R have positive entropy change.