RRB ALP CBT I 25 Nov 2024 Shift 1 Paper

Concept:This is a redox reaction where $\mathrm{CuO}$ is reduced to $\mathrm{Cu}$ and $\mathrm{NH}_3$ is oxidized to $\mathrm{N}_2$.Explanation:Start with the unbalanced equation: $\mathrm{CuO} + \mathrm{NH}_3 \rightarrow \mathrm{Cu} + \mathrm{N}_2 + \mathrm{H}_2\mathrm{O}$.Balance nitrogen first: 2 $\mathrm{NH}_3$ gives 1 $\mathrm{N}_2$.Balance hydrogen: 2 $\mathrm{NH}_3$ gives 6 H atoms, so 3 $\mathrm{H}_2\mathrm{O}$ are needed on the product side.Balance oxygen: 3 $\mathrm{H}_2\mathrm{O}$ contain 3 O atoms, so 3 $\mathrm{CuO}$ are needed on the reactant side.Now balance copper: 3 $\mathrm{CuO}$ gives 3 $\mathrm{Cu}$.Check all atoms: Reactants: 3 Cu, 3 O, 2 N, 6 H.Products: 3 Cu, 3 O, 2 N, 6 H.The equation is balanced: $$3\mathrm{CuO} + 2\mathrm{NH}_3 \rightarrow 3\mathrm{Cu} + \mathrm{N}_2 + 3\mathrm{H}_2\mathrm{O}.$$Answer:Option C: $3\mathrm{CuO} + 2\mathrm{NH}_3 \rightarrow 3\mathrm{Cu} + \mathrm{N}_2 + 3\mathrm{H}_2\mathrm{O}$.