• # question_answer 6) 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)$2N{{O}_{2}}+2O{{H}^{-}}(aq)\to NO_{2}^{-}(aq)+NO_{3}^{-}(aq)+{{H}_{2}}O(l)$

(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.