question_answer 1)

Suggest a scheme of classification of the following redox reactions: (a) \[{{N}_{2}}(g)+{{O}_{2}}(g)\to 2NO(g)\] (b) \[2Pb{{(N{{O}_{3}})}_{2}}(s)\to 2PbO(s)+2N{{O}_{2}}(g)+\frac{1}{2}{{O}_{2}}(g)\] (c) \[NaH(s)+{{H}_{2}}O(l)\to NaOH(aq)+{{H}_{2}}(g)\] (d)\[2N{{O}_{2}}+2O{{H}^{-}}(aq)\to NO_{2}^{-}(aq)+NO_{3}^{-}(aq)+{{H}_{2}}O(l)\]

Answer:

(a) \[\overset{0}{\mathop{{{N}_{2}}}}\,(g)+\overset{0}{\mathop{{{O}_{2}}}}\,(g)\to \overset{+2-2}{\mathop{2NO}}\,(g)\] It is a combination (combustion) type of redox reaction. (b) \[2\overset{+2}{\mathop{Pb}}\,\overset{+5-2}{\mathop{{{(N{{O}_{3}})}_{2}}}}\,(s)\to \overset{+2-2}{\mathop{2PbO(s)}}\,+2\overset{+4-2}{\mathop{N{{O}_{2}}(g)}}\,+\frac{1}{2}\overset{0}{\mathop{{{O}_{2}}}}\,(g)\] It is also a redox reaction involving decomposition of lead nitrate. (c) \[\overset{+1-1}{\mathop{NaH(s)}}\,+\overset{+1-2}{\mathop{{{H}_{2}}O(l)}}\,\to \overset{+1-2+1}{\mathop{NaOH}}\,(aq)+\overset{0}{\mathop{{{H}_{2}}}}\,(g)\] It is a displacement type of redox reaction in which hydrogen of water is displaced by a hydride ion into dihydrogen gas. (d)\[2\,\overset{+4}{\mathop{N}}\,{{\overset{-2}{\mathop{O}}\,}_{2}}+2\overset{-2}{\mathop{O}}\,\overset{+1}{\mathop{{{H}^{-}}\to }}\,\overset{+3}{\mathop{N}}\,\overset{-2}{\mathop{O_{2}^{-}}}\,\,(aq)+\overset{+5}{\mathop{N}}\,\overset{-2}{\mathop{O_{3}^{-}}}\,\,(aq)\]\[+{{H}_{2}}O(l)\] It is disproportionation in which the oxidation state of nitrogen changes from +4 to +3 and +5.