JEE Advance - Chemistry (2008 - Paper 1 Offline - No. 10)
A solution of colourless salt H on boiling with excess NaOH produces a non-flammable gas. The gas evolution ceases after sometime. Upon addition of Zn dust to the same solution, the gas evolution restarts. The colourless salt(s) H is(are):
NH$$_4$$NO$$_3$$
NH$$_4$$NO$$_2$$
NH$$_4$$Cl
(NH$$_4$$)$$_2$$SO$$_4$$
Explanation
The colourless salt H is either NH$$_4$$NO$$_3$$ or NH$$_4$$NO$$_2$$. The colourless salt produces NH$$_3$$ gas (non-inflammable) on boiling with excess of NaOH. On addition of zinc dust (a reducing agent) to this solution, sodium nitrite or sodium nitrate will liberate NH$$_3$$ gas again.
NH$$_4$$NO$$_3$$ + NaOH $$\to$$ NH$$_3$$ + NaNO$$_3$$ + H$$_2$$O
7NaOH + NaNO$$_3$$ + 4Zn $$\to$$ 4Na$$_2$$ZnO$$_2$$ + NH$$_3$$ + 2H$$_2$$O
NH$$_4$$NO$$_2$$ + NaOH $$\to$$ NaNO$$_2$$ + NH$$_3$$ + H$$_2$$O
3Zn + 5NaOH + NaNO$$_2$$ $$\to$$ 3Na$$_2$$ZnO$$_2$$ + NH$$_3$$
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