Q. Which of the following acids will have lowest value of $pK_{a}$?
A) ${CH}_{3}{CH}_{2}COOH$
B) ${CH}_{3}CHCOOH$
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Br
C) ${CH}_{3}CHCOOH$
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F
D) ${FCH}_{2}{CH}_{2}COOH$
Explanation
(a)
$pK_{a} \propto \frac{1}{K_{a}}$
Stronger the acid, higher the $K_{a}$ value and lower the $pK_{a}$ value.
The order of acidity of given acids is as
${CH}_{3}CHCOOH > {CH}_{3}CHCOOH$ >${FCH}_{2}{CH}_{2}COOH > {CH}_{3}{CH}_{2}COOH$
| |
F Br
Since, ${CH}_{3}{CH}_{2}COOH$ is the weakest acid among the given, its $pK_{a}$ value will be highest.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.