question_answer

Assign reasons for each of the following : (i) + 1 gallium undergoes disproportionation reactions. (ii) Unlike \[\text{I}{{n}^{+}},\,\text{T}{{\text{l}}^{+}}\] is more stable with respect to disproportionation. (iii) \[\text{InCl}\] undergoes disproportionation but \[\text{TlCl}\] does not. (iv) In \[(III)\] is more stable than In \[(I)\] in aqueous solution.

Answer:

                (i) Due to inert pair effect, gallium shows both +1 and +3 oxidation states but its +3 oxidation state is more stable than +1 oxidation state. In other words, +1 gallium is less stable than +3 gallium and hence undergoes disproportionation (self oxidation-reduction) to form gallium metal and the more stable +3 gallium ions in aqueous solution as shown below: or            \[3\,G{{a}^{+}}\,(aq)\xrightarrow{\,}2\,Ga(s)+G{{a}^{3+}}(aq)\] (ii) Although both \[\text{In}\]and \[\text{Tl}\] can show oxidation states of + 1 and + 3, but inert pair effect is more prominent in \[\text{Tl}\] than in \[\text{In}\]. Therefore, + 1 oxidation state of \[\text{Tl}\] is more stable than its + 3 oxidation state while + 3 oxidation state of \[\text{In}\] is more stable than its + 1 oxidation state. Consequently, in aqueous solution, less stable \[\text{I}{{\text{n}}^{+}}\] undergoes disproportionation to form more state \[\text{I}{{\text{n}}^{3+}}\] but + 1 thallium being more stable does not undergo disproportionation to form + 3 thallium.   (iii) As stated above, + 3 oxidation state of \[\text{In}\] is more stable than its + 1 oxidation state, therefore, \[\text{InCl}\]undergoes disproportionation in aqueous solution. \[\text{3}\,\text{InCl}\,\text{(aq)}\,\xrightarrow{\,}\,2\,\text{I}n\,(s)+\,\text{I}{{n}^{3+}}\,(aq)\]\[+3\,\text{C}{{\text{l}}^{-}}\,(aq)\] Since +1 oxidation state of \[\text{Tl}\] is more stable than its +3 oxidation state, therefore, \[\text{TlCl}\]does not undergo disproportionation in aqueous solution.   (iv) Same as explained in answer (ii) above.