Question

Arrange the following acids in decreasing order of their $p{K}_a$ values

• A. IV, III, II, I
• B. II, I, IV, III
• C. II, I, III, IV
• D. I, II, IV, III

Answer 1

Answer: (C)

The acidity increases on decreasing the value of $p{K}_a$ . $\underset{aceticacid}{C{H}_{3}COOH}<\underset{formicacid}{\mathrm{HCOOH}}<\underset{chloroaceticacid}{ClC{H}_{2}COOH}$ $<\underset{\begin{array}{c}trichloroacetic\\ acid\end{array}}{C{l}_{3}C.COOH}$ $\underset{Increasingorderofacidicstrength}{\to }$ or Decreasing order of $p{K}_a$ .