Given below are two statements, one is labelled as Assertion A and the other is labelled as Reason R.
Assertion A : Order of acidic nature of the following compounds is A > B > C.
Reason R : Fluoro is a stronger electron withdrawing group than Chloro group.
In the light of the above statements, choose the correct answer from the options given below:

Solution

Chemistry ma’am · 5 steps

Both statements are true, but if fluorine's pull decided it, B would beat A. Position wins here.

1. Read the compounds. The rings are benzene rings, so all three are phenols. A is 2-chlorophenol, B is 4-fluorophenol and C is 3-methylphenol (m-cresol).
2. What sets acidity. A phenol is more acidic when its phenoxide ion is more stable. Electron-withdrawing effects near the oxygen stabilise the ion. Electron-donating effects destabilise it.

   Phenol	Effect on the phenoxide	Approx. pKₐ
   A: ortho-Cl	Strong -I, acting from very close to the O	8.5, most acidic
   B: para-F	Weak -I from far away, largely cancelled by strong +R (2p–2p overlap)	9.9
   C: meta-CH₃	+I donates electrons, so the ion is destabilised	10.1, least acidic

3. Check each statement. So A > B > C, and Assertion A is true. Fluorine is more electronegative than chlorine, so it withdraws more strongly by induction, and Reason R is true.
4. Does R explain A. No. If fluorine's stronger pull decided the order, B would be more acidic than A. A wins because chlorine sits at the ortho position, close to the O–H, while para-fluorine also gives electrons back by +R.
5. So. Both A and R are correct, but R is not the correct explanation of A. The answer is (a).

The idea to keep. For substituted phenols, check the position before the electronegativity. Ortho -I acts right next to the O–H. A para halogen also pushes electrons back by +R, and fluorine's +R is strong.

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