IIT-JEE 2008 · Paper 1 · Chemistry Q55

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ChemistryMultiple correct+4 / -1Question 55 of 69

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)

\ce{NH4NO3}

\ce{NH4NO2}

\ce{NH4Cl}

\ce{(NH4)2SO4}

Answer and worked solution

Official answer: A, B

First gas. Any ammonium salt boiled with NaOH gives $\ce{NH3}$ (non-flammable), until the $\ce{NH4+}$ is used up.

Restart with zinc. Zn in alkali reduces nitrate or nitrite to more ammonia:
$\ce{NO3- + 4Zn + 7OH- -> NH3 + 4ZnO2^{2-} + 2H2O},$
and likewise for $\ce{NO2-}$ . Chloride and sulphate are not reduced.

(A), (B)

Topics:Anion analysis Cation analysis

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IIT-JEE 2008 · Paper 1, Chemistry question 55