Ncert Exercises & Solutions

Select the correct option based on statements below:

Assertion (A):	NaCl reacts with concentrated H₂SO₄ to give colourless fumes with a pungent smell. But on adding MnO₂, the fumes become greenish-yellow
Reason (R):	MnO₂ oxidizes HCl to chlorine gas which is greenish-yellow.

1.	Both (A) and (R) are true and (R) is the correct explanation of (A).
2.	Both (A) and (R) are true but (R) is not the correct explanation of (A).
3.	(A) is true but (R) is false.
4.	(A) is false but (R) is true.

HINT: Colourless fumes with a pungent smell gas is HCl

Explanation:

NaCl reacts with concentrated H₂SO₄to give colourless fumes with a pungent smell.

The pungent smell is due to the formation of HCl. The reaction is as follows:

NaCl + H_{2} {SO}_{4} \to {Na}_{2} {SO}_{4} + 2 HCl

But on adding MnO₂ the fumes become greenish-yellow due to the formation of chlorine gas. MnO₂ oxidised Cl^- into Cl₂.

The reaction is as follows:

MnO₂ + 4HCl → MnCl₂ + 2H₂O + Cl₂