Question

A certain buffer solution contains equal concentration of $X^{-}$ and $HX$. The $K_b$ for $X^{-}$ is ${10}^{-10}$. The $pH$ of the buffer is:
(correct answer +1, wrong answer -0.25)

• A. $4$
• B. $7$
• C. $10$
• D. $14$

Answer 1

The correct option is A $4$

For a basic buffer,
$pH=14-p{K}_b-log\frac{\left[Salt\right]}{\left[Base\right]}$
$pH=14-(-log{10}^{-10})-log1$
$\Rightarrow pH=4$