JEE Main 2022 · 28 July · morning · Single correct · +4 / −1
Match List - I with List - II, match the gas evolved during each reaction.
Choose the correct answer from the options given below :
| List - I | List - II | ||
|---|---|---|---|
| (A) | (NH₄)₂ Cr₂ O₇ →(Δ) | (I) | H₂ |
| (B) | KMnO₄+HCl → | (II) | N₂ |
| (C) | Al+NaOH+H₂ O → | (III) | O₂ |
| (D) | NaNO₃ →(Δ) | (IV) | Cl₂ |
- (a) (A)-(II),(B)-(III),(C)-(I),(D)-(IV)
- (b) (A)-(III),(B)-(I),(C)-(IV),(D)-(II)
- (c) (A)-(II),(B)-(IV),(C)-(I),(D)-(III)
- (d) (A)-(III),(B)-(IV),(C)-(I),(D)-(II)
Answer and solution
Answer (c) (A)-(II),(B)-(IV),(C)-(I),(D)-(III)
Solution
Chemistry ma’am · 2 steps
Ask what gets oxidised in each reaction, and the gas follows: N2, Cl2, H2, O2.
- Find the change. In each reaction, look for the element that changes its oxidation state and ends up as a gas. That element tells you which gas comes off.
Reaction What happens Gas (A) (NH₄)₂Cr₂O₇ →(Δ) Dichromate oxidises its own NH₄⁺ (N goes from -3 to 0): (NH₄)₂Cr₂O₇ → N₂ + Cr₂O₃ + 4H₂O N₂ (II) (B) KMnO₄ + HCl Permanganate oxidises chloride: 2KMnO₄ + 16HCl → 2KCl + 2MnCl₂ + 5Cl₂ + 8H₂O Cl₂ (IV) (C) Al + NaOH + H₂O Amphoteric Al dissolves in alkali: 2Al + 2NaOH + 6H₂O → 2Na[Al(OH)₄] + 3H₂ H₂ (I) (D) NaNO₃ →(Δ) An alkali metal nitrate only goes down to the nitrite: 2NaNO₃ → 2NaNO₂ + O₂ O₂ (III) - So. The matching is (A)-(II), (B)-(IV), (C)-(I), (D)-(III), which is option (c).
The idea to keep. Ammonium dichromate gives N₂, and alkali metal nitrates stop at the nitrite and give only O₂. When an oxidising agent meets HCl, expect Cl₂.
Answer from the NTA final answer key. Solution by PrepWiser.