Nitrogen gas is obtained by thermal decomposition of :

Solution

Chemistry ma’am · 3 steps

Look for the compound whose nitrogen is already bonded only to nitrogen: azides break straight into N₂.

1. Azide gives nitrogen. In Ba(N₃)₂ each azide ion N₃⁻ is three nitrogen atoms joined together, with no oxygen at all. On gentle heating it falls apart into barium metal and very pure N₂.

   Ba(N₃)₂ →(Δ) Ba + 3N₂

2. Nitrates and nitrites. In nitrates and nitrites, nitrogen is bonded to oxygen. Heating them releases O₂ or oxides of nitrogen, not N₂.

   Compound	On heating	Gas released
   Ba(NO₃)₂	2Ba(NO₃)₂ → 2BaO + 4NO₂ + O₂	NO₂ and O₂
   Ba(N₃)₂	Ba(N₃)₂ → Ba + 3N₂	pure N₂
   NaNO₂	stable to high temperature, then gives Na₂O	oxides of nitrogen
   NaNO₃	2NaNO₃ → 2NaNO₂ + O₂	O₂

3. So. Only barium azide, option (b), gives nitrogen gas on thermal decomposition.

The idea to keep. For very pure N₂ in the lab, heat an azide like NaN₃ or Ba(N₃)₂. Metal nitrates and nitrites give O₂ or nitrogen oxides instead.

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