Suggest a scheme of classification of the following redox reactions: (a) N₂(g) + O₂(g) → 2 NO(g) (b) 2Pb(NO₃)₂(s) → 2PbO(s) + 4NO₂(g) + O₂(g) (c) NaH(s) + H₂O(l) → NaOH(aq) + H₂(g) (d) 2NO₂(g) + 2OH⁻(aq) → NO₂⁻(aq) + NO₃⁻(aq) + H₂O(l)
Combination redox reaction: The compound nitric oxide is formed by the combination of the elemental substances, nitrogen and oxygen.
Decomposition redox reaction: The reaction involves the breaking down of lead nitrate into three components.
Displacement redox reaction: Hydrogen of water has been displaced by hydride ion into dihydrogen gas.
Disproportionation redox reaction: The reaction involves disproportionation of (+4 state) into (+3 state) and (+5 state).
Explanation
The classification of redox reactions is based on the structural changes occurring during the reaction. Reaction (a) is a combination as two elements form a single compound. Reaction (b) is a decomposition as a single compound breaks into multiple products. Reaction (c) is a displacement because one element (hydride ion) displaces another (hydrogen in water). Reaction (d) is a disproportionation because the same element (nitrogen in ) is simultaneously oxidized and reduced to different oxidation states.