When MnO₂ and H₂ SO₄ is added to a salt (A), the greenish yellow gas liberated as salt (A) is :

Solution

Chemistry ma’am · 3 steps

Greenish yellow gas means chlorine, so look for the salt that carries a chloride ion.

1. Name the gas. Chlorine is the only common gas in salt analysis that is greenish yellow. So salt (A) must contain the Cl⁻ ion.
2. What MnO2 does. Concentrated H₂SO₄ supplies the acid, and MnO₂ acts as an oxidising agent. It oxidises a halide ion to the free halogen, and each halogen has its own colour.

   MnO₂ + 4H⁺ + 2Cl⁻ → Mn²⁺ + 2H₂O + Cl₂ ↑

   Salt	Anion	Gas or vapour released	Colour
   NH₄Cl	Cl⁻	Cl₂	greenish yellow
   CaI₂	I⁻	I₂ vapour	violet
   KNO₃	NO₃⁻	no halogen; with conc. H₂SO₄ on heating, NO₂	light brown
   NaBr	Br⁻	Br₂ vapour	reddish brown

3. So. Only NH₄Cl gives chlorine: 2NH₄Cl + MnO₂ + 2H₂SO₄ → (NH₄)₂SO₄ + MnSO₄ + 2H₂O + Cl₂. Salt (A) is option (a).

The idea to keep. With MnO₂ and conc. H₂SO₄, the halide shows its colour: chloride gives greenish yellow Cl₂, bromide gives reddish brown Br₂, iodide gives violet I₂.

Answer from the NTA final answer key. Solution by PrepWiser.