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Which of the following reactions is a redox reaction? (A) 2NaAg(CN)2 + Zn -> Na2Zn(CN)4 + 2Ag (B) BaO2 + H2SO4 -> BaSO4 + H2O2 (C) N2O5 + H2O -> 2HNO3 (D) AgNO3 + KI -> AgI + KNO3
- 2NaAg(CN)2 + Zn -> Na2Zn(CN)4 + 2Ag
- BaO2 + H2SO4 -> BaSO4 + H2O2
- N2O5 + H2O -> 2HNO3
- AgNO3 + KI -> AgI + KNO3
Correct answer: 2NaAg(CN)2 + Zn -> Na2Zn(CN)4 + 2Ag
Solution
In reaction A, Zn (0) is oxidised to Zn (+2) while Ag (+1) is reduced to Ag (0) — clear electron transfer. The other reactions involve only double decomposition or no oxidation-state changes.
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