The correct stability order of the following diazonium salt is

Solution

Chemistry ma’am · 3 steps

A diazonium ion is a cation, so electron-donating groups stabilise it and withdrawing groups do the opposite.

1. Where the charge sits. The N₂⁺ group is positively charged and pulls electron density out of the benzene ring. A para group that pushes electrons into the ring spreads this positive charge out and stabilises the ion. A group that pulls electrons concentrates the charge and destabilises it.

   Salt	Para group	Effect on the ring	Stability
   (A)	OCH₃	+R from the O lone pair, which outweighs its -I	highest
   (C)	H	none, the reference	second
   (D)	CN	-R and -I	third
   (B)	NO₂	strongest -R and -I	lowest

2. Nitro versus cyano. Both are withdrawing groups, but NO₂ pulls electrons more strongly than CN. So the nitro salt is the least stable of the two.
3. So. The order is (A) > (C) > (D) > (B), which is option (b).

The idea to keep. For any cation on a benzene ring, rank by electron donation: +R donors such as OCH₃ stabilise most, H is the reference, and stronger withdrawers such as NO₂ destabilise most.

Answer from the NTA final answer key. Solution by PrepWiser.