Question

$p{K}_a$ of weak acid is 3.0 . Effective range of a buffer of $HA$ and $A^{-}$ is :

• A. 3 to 4
• B. 4 to 6
• C. 2 to 3
• D. 2 to 4

Answer 1

The correct option is D 2 to 4

Range of Buffer solution is $\left[\right(p{K}_a-1),(p{K}_a+1\left)\right]$.
As $p{K}_a=3$
So, $p{K}_a-1=3-1=2$
and $p{K}_a+1=3+1=4$
$\therefore$ effective range of a buffer $HA$ and $A^{-}$ is $[2,4]$ i.e., from 2 to 4.