Question

Which one of the following has $△S^{\circ }$ greater then zero?

• A. $CaO\left(s\right)+C{O}_2\left(g\right)\rightleftharpoons CaC{O}_3\left(s\right)$
• B. $NaCl\left(aq\right)\rightleftharpoons NaCl\left(s\right)$
• C. $NaN{O}_3\left(s\right)\rightleftharpoons N{a}^{+}\left(aq\right)+N{O}_3^{-}\left(aq\right)$
• D. $N_2\left(g\right)+3H_2\left(g\right)\rightleftharpoons 2N{H}_3\left(g\right)$

Answer 1

The correct option is C $NaN{O}_3\left(s\right)\rightleftharpoons N{a}^{+}\left(aq\right)+N{O}_3^{-}\left(aq\right)$

Order of randomness: Gas > Liquid > Solid
(i) In (b), product NaCl (solid) has lesser entropy as compared to NaCl(aq) ($N{a}^{+}$ and or) in reactant.
(ii)In (a), product (solid) has lesser entropy as compared to reactants.
(iii) In (d), both reactants and products are in gaseous state, but numberof moles or products are decreasing.
(iv) In (c), products are in liquid state hence high entropy than reactant which is present in solid state.