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An inorganic salt when heated with concentrated evolves a colorless pungent-smelling gas. However, wQualitative and Quantitative Analysis Chemistry Question

Question

An inorganic salt when heated with concentrated $H_2SO_4$ evolves a colorless pungent-smelling gas. However, when the same salt is heated with a mixture of concentrated $H_2SO_4$ and $MnO_2$, it evolves a colored pungent-smelling gas that bleaches moist litmus paper. The colored gas is:

Answer: B

💡 Solution & Explanation

The salt is a chloride. Heating a chloride salt with concentrated $H_2SO_4$ yields $HCl$, a colorless pungent gas. When $MnO_2$ (an oxidizing agent) is added along with $H_2SO_4$, the $HCl$ formed is oxidized to chlorine gas ($Cl_2$). Chlorine is a yellowish-green, pungent-smelling gas that effectively bleaches moist litmus paper via oxidation. $NO_2, Br_2$, and $I_2$ do not bleach litmus paper in this characteristic manner.

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