• # question_answer 27) Consider the reactions: (a) ${{H}_{3}}P{{O}_{2}}(aq)+4AgN{{O}_{3}}(aq)+2{{H}_{2}}O(l)$ $\to \,{{H}_{3}}P{{O}_{4}}(aq)+4Ag(s)+4HN{{O}_{3}}(aq)$ (b) ${{H}_{3}}P{{O}_{2}}(aq)+2CuS{{O}_{4}}(aq)+2{{H}_{2}}O(l)$ $\to {{H}_{3}}P{{O}_{4}}(aq)+2Cu(s)+{{H}_{2}}S{{O}_{4}}(aq)$ (c) ${{C}_{6}}{{H}_{5}}CHO(l)+2{{[Ag{{(N{{H}_{3}})}_{2}}]}^{+}}(aq)+3O{{H}^{-}}\to$${{C}_{6}}{{H}_{5}}CO{{O}^{-}}(aq)+2Ag(s)+4N{{H}_{3}}(aq)+2{{H}_{2}}O(l)$(d) ${{C}_{6}}{{H}_{5}}CHO(l)+2C{{u}^{2+}}(aq)+\underset{No\,change\,observed.}{\mathop{5O{{H}^{-}}(aq)\to }}\,$ What inference do you draw about the behaviour of and $C{{u}^{2+}}$from these reactions?

(a) ${{H}_{3}}P{{O}_{2}}(aq)+4\overset{+1}{\mathop{AgN{{O}_{3}}}}\,(aq)+2{{H}_{2}}O(l)\to$${{H}_{3}}P{{O}_{4}}(aq)+4Ag(s)+4HN{{O}_{3}}(aq)$ $A{{g}^{+}}$ion is reduced to , thus $Ag$ acts as an oxidising agent, it oxidises ${{H}_{3}}P{{O}_{2}}$ to ${{H}_{3}}P{{O}_{4}}$ (b) ${{H}_{3}}P{{O}_{2}}(aq)+2\overset{2+}{\mathop{CuS{{O}_{4}}}}\,(aq)+2{{H}_{2}}O(l)\to$${{H}_{3}}P{{O}_{4}}(aq)+2\overset{0}{\mathop{Cu}}\,(s)+{{H}_{2}}S{{O}_{4}}(aq)$ $C{{u}^{2+}}$ion is reduced to$Cu(s)$, thus $C{{u}^{2+}}$ acts as oxidising agent, it oxidises ${{H}_{3}}P{{O}_{2}}$ to ${{H}_{3}}P{{O}_{4}}$. (c)${{C}_{6}}{{H}_{5}}CHO(l)+2{{[\overset{+1}{\mathop{Ag}}\,{{(N{{H}_{3}})}_{2}}]}^{+}}(aq)+3O{{H}^{-}}(aq)$$\to {{C}_{6}}{{H}_{5}}CO{{O}^{-}}+2Ag(s)+4N{{H}_{3}}(aq)+2{{H}_{2}}O(l)$ In above reaction, $A{{g}^{+}}$ ion is reduced to $Ag(s)$thus it acts as an oxidising agent; it oxidises ${{C}_{6}}{{H}_{5}}CHO$to${{C}_{6}}{{H}_{5}}CO{{O}^{-}}(aq).$. (d) ${{C}_{6}}{{H}_{5}}CHO(l)+2C{{u}^{2+}}+5O{{H}^{-}}\to$ No change. It is not a redox reaction.