Question

Calculate the pH of a solution that is 2.00 M HF, 1.00 M NaOH, and 0.472 M NaF. (Ka=7,2×104)

Answer 1

Explanation:

The given data is as follows.

Concentration of acid, [HF] = 2 M

Concentration of salt, [NaF] = 0.472 M

Concentration of base, [NaOH] = 1.00 M

$K_{a}$ = $7.2 \times 10^{-4}$

So, NaOH being a base will react with the acid that is, HF. And, according to Henderson-Hasselbalch equation we have he following.

             pH = $pK_{a} + log\frac{[salt]}{[acid]}$

Also, we known that $pK_{a} = -log K_{a}$

so,                     $pK_{a} = -log 7.2 \times 10^{-4}$

                         $pK_{a}$ = 3.1426

Hence,    pH = $3.1426 + log\frac{0.472 M}{2 M}$

               pH = 2.5155

Thus, we can conclude that pH of the solution is 2.5155.