Question

Following is the titration curve of two acids $HA$ and $HB$ (5 milli-moles each) titrated against strong base $NaOH\left(0.1M\right)$.
What is $p{K}_a$ for $HB$ acid?

• A. 3
• B. 4
• C. 5
• D. 6

Answer 1

Answer: (C)

5

As we know, at half point of equivalence point

$pH=pKa$ and from figure it can be seen that at half point

$pH=5$ for HB so its pKa is 5.