JEE Advanced 2022 Paper 1, Chemistry Section 2 Q4: Oxidation and Reduction

Galena is lead(II) sulphide, PbS. With dilute HNO${}_3$:

$3\text{PbS}+8{\text{HNO}}_3\to 3{\text{Pb(NO}}_3{)}_2+2\text{NO}\uparrow +3\text{S}+4{\text{H}}_2\text{O}$

The gas evolved is nitric oxide (NO).

(A) NO has 11 valence electrons (odd-electron molecule) with one unpaired electron in a ${\pi }^{\ast }$ orbital, making it paramagnetic. Correct.

(B) NO is diatomic, so it is linear by definition, not bent. Wrong.

(C) NO is a neutral oxide; it does not react with water to give an acid, nor with bases. Wrong.

(D) NO is colourless at room temperature (it turns brown when oxidised by air to NO${}_2$). Correct.