Q. The pH value of an acid is 5 and its concentration is 1 M. What is the value of $K_{a}$ for the acid?
A) $10^{- 7}$
B) $10^{- 5}$
C) $10^{- 10}$
D) $10^{- 8}$
Explanation
(c)
By using pH=$- \log\sqrt{K_{a}.C}$
$5 = - \log\sqrt{K_{a} \times 1} = - \frac{1}{2}\log K_{a}$
$\log{K_{a} = - 10}$
$K_{a} = 10^{- 10}$
Hence, dissociation constant $\left( K_{a} \right) = 10^{- 10}$.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.