Question

Buffer capacity is maximum when the ratio of $\left[salt\right]$:$\left[acid\right]$ is ___.

• A. 1:2
• B. 1:10
• C. 10:1
• D. 1:1

Answer 1

The correct option is D 1:1

Buffer capacity is a measure of the efficiency of a buffer in resisting changes in pH. Conventionally, the buffer capacity is expressed as the amount of strong acid or base, in gram-equivalents, that must be added to 1 liter of the solution to change its pH by one unit.

Calculate the buffer capacity as: $=\frac{\Delta B}{\Delta pH}$

$\Delta B=$gram equivalent of strong acid/base to change pH of 1 liter of buffer solution

$\Delta pH=$ the pH change caused by the addition of strong acid/baseleft to drive the reaction

The buffer capacity is optimal when the ratio is $1:1$; that is, when $pH=pKa$