Why does a good buffer have a pH close to pKa?

When the pH is equal to the pKa, you have high concentrations of both conjugate acid and conjugate base. You need the weak base to react with added acid, and the weak acid to react with added base to stabilize the pH.

What is the relationship of pH and pKa in buffers?

The lower the pH, the higher the concentration of hydrogen ions [H+]. The lower the pKa, the stronger the acid and the greater its ability to donate protons.

Why do we use pH buffer solution in titration?

A buffer solution is used in EDTA titration because it resists the change in pH. This is because all the reactions between the metal ions and EDTA are pH-dependent.

Why is it best to use an acidic buffer system to maintain a pH value that is within 1 pH unit of the pKa of the weak acid?

A rule-of-thumb is to use a buffer within 1 pH unit of the pKa to maximize its buffering capacity (see the Henderson-Hasselbach equation provided by Aziz Habibi-Yangjeh for the math). If no acid or base is going to be added, then the pH will not change from where it started, so the weak buffering isn’t a problem.

What happens when pKa equals pH?

This means that when the pH is equal to the pKa there are equal amounts of protonated and deprotonated forms of the acid. For example, if the pKa of the acid is 4.75, at a pH of 4.75 that acid will exist as 50\% protonated and 50\% deprotonated.

What makes a buffer effective?

A buffer is most effective when the amounts of acid and conjugate base are approximately equal. As a general rule of thumb, the relative amounts of acid and base should not differ by more than tenfold.

How does buffer concentration affect buffer capacity?

Buffer capacity is the measure of a buffer’s ability to resist pH change. This ability depends on the concentration of the buffer components, meaning the acid and its conjugate base. A higher buffer concentration has a greater buffer capacity.