The gas produced by treating an aqueous solution of ammonium chloride with sodium nitrite is :

Solution

Chemistry ma’am · 4 steps

Swap the partners first: you get ammonium nitrite, and on warming it falls apart into N₂ and water.

1. Double decomposition. In water, NH₄⁺ from ammonium chloride pairs with NO₂⁻ from sodium nitrite. This forms ammonium nitrite, and NaCl stays in solution.
2. Ammonium nitrite breaks down. NH₄NO₂ is unstable. On gentle warming it decomposes into dinitrogen and water. This is the standard laboratory preparation of N₂.

   NH₄Cl(aq) + NaNO₂(aq) → N₂(g) + 2H₂O(l) + NaCl(aq)

3. Why nitrogen gas. Nitrogen in NH₄⁺ is at -3 and nitrogen in NO₂⁻ is at +3. They meet in the middle at 0, which is N₂.
4. So. The gas given off is dinitrogen, N₂, option (b).

The idea to keep. An ammonium salt plus a nitrite gives NH₄NO₂, which decomposes to N₂. Heating NH₄NO₃ gives N₂O instead, so look at the anion before you answer.

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