Question

A buffer contains the weak acid HA and its conjugate base A−. The weak acid has a pKa of 4.82 and the buffer has a pH of 4.25. Then, [HA] > [A^-]. True or False?

Answer 1

Answer:

True

Explanation:

Given:

pKa of weak acid = 4.82

pH of buffer = 4.25

Now, put the values in Henderson-Hasselbalch equation

$pH=p_{Ka} + log\frac{[Salt]}{[Acid]}$

$4.25=4.82 + log\frac{[A^{-}]}{[HA]}$

$log\frac{[A^{-}]}{[HA]} = -0.57$

$\frac{[A^{-}]}{[HA]} = 0.269$

0.269 is less than 1.

therefore, [HA] is greater than [A-].

Hence, the given statement is true.