Match the acids with their approximate pKa values. Acids: P: CH3COOH; Q: ClCH2COOH; R: Cl2CHCOOH; S: Cl3CCOOH. pKa values: 1: 0.7; 2: 1.3; 3: 2.9; 4: 4.8.

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JEE Advanced levelSingle correct optionDifficulty 3 of 3g1019

Match the acids with their approximate pKa values. Acids: P: $CH X_{3} COOH$ ; Q: $ClCH X_{2} COOH$ ; R: $Cl X_{2} CHCOOH$ ; S: $Cl X_{3} CCOOH$ . pKa values: 1: 0.7; 2: 1.3; 3: 2.9; 4: 4.8.

AP-1, Q-2, R-3, S-4
BP-4, Q-3, R-1, S-2
CP-4, Q-3, R-2, S-1
DP-3, Q-4, R-2, S-1

Answer: C

Each added Cl increases the total -I effect and lowers the pKa. The order of acidity is S > R > Q > P, so S has the lowest pKa (0.7), R 1.3, Q 2.9 and P (acetic acid) 4.8. This gives P-4, Q-3, R-2, S-1.

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Match the acids with their approximate pKa values. Acids: P: CHX3​COOH; Q: ClCHX2​COOH; R: ClX2​CHCOOH; S: ClX3​CCOOH. pKa values: 1: 0.7; 2: 1.3; 3: 2.9; 4: 4.8.

Answer: C

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Match the acids with their approximate pKa values. Acids: P: $CH X_{3} COOH$ ; Q: $ClCH X_{2} COOH$ ; R: $Cl X_{2} CHCOOH$ ; S: $Cl X_{3} CCOOH$ . pKa values: 1: 0.7; 2: 1.3; 3: 2.9; 4: 4.8.