For the given compounds, the correct order of increasing pKₐ value :
Choose the correct answer from the options given below :

Solution

Chemistry ma’am · 3 steps

Lower pKa means stronger acid, so rank by how well each group stabilises the phenoxide ion.

1. What decides pKa. Phenol loses H⁺ to give a phenoxide ion. A group that pulls electron density away spreads the negative charge and stabilises the ion, so the acid is stronger and its pKa is lower. A group that pushes electrons in does the reverse.
2. Position matters. Resonance effects act only from the ortho and para positions. From the meta position a group acts mainly through its weaker inductive effect. So a group at para has a bigger effect than the same group at meta, in whichever direction it pushes.

   Compound	Group and position	Effect on phenoxide	pKa
   (B)	-NO₂, para	−R and −I, strongly stabilises	lowest
   (D)	-NO₂, meta	−I only, stabilises less	low
   (A)	none	reference	middle
   (C)	-OCH₃, meta	no +R from meta, small effect	high
   (E)	-OCH₃, para	+R pushes charge onto the ring, destabilises most	highest

3. So. Increasing pKa runs from the strongest acid to the weakest: (B) < (D) < (A) < (C) < (E), which is option (b).

The idea to keep. Electron-withdrawing groups lower pKa and electron-donating groups raise it. The effect is strongest at para (resonance plus induction) and weaker at meta (induction alone).

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