Q.Answer the following question.
In which reaction does nitrogen exhibit variation of oxidation state from -3 to +5?
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Start your 14-day free trial to unlock the full solution →Step 1. Find nitrogen's oxidation number in NH3. H is +1 (bonded to non-metal N), 3 H give +3; ON(N) + 3(+1) = 0, so ON(N) = -3.
Step 2. Find nitrogen's oxidation number in HNO3. H is +1, O is -2 (x3 = -6); (+1) + ON(N) + (-6) = 0, so ON(N) = +5.
Step 3. Identify the reaction connecting them. There is no single-step reaction taking NH3 directly to HNO3; industrially this is done by the Ostwald process, a three-stage catalytic oxidation. Stage 1: ammonia is catalytically oxidised to nitric oxide, 4NH3(g) + 5O2(g) → 4NO(g) + 6H2O(g), where N rises from -3 to +2. Stage 2: nitric oxide is further oxidised, 2NO(g) + O2(g) → 2NO2(g), where N rises from +2 to +4. Stage 3: nitrogen dioxide is absorbed in water to give nitric acid, 3NO2(g) + H2O(l) → 2HNO3(aq) + NO(g), where most of the N reaches +5 (in HNO3), with a little NO, at +2, r …
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