Generally, dilution has NO effect on the pH. Why is this so? If you look at the buffer formula, pH = pKa + lg [salt]/[acid], dilution does not affect the [salt]/[acid] ratio. i.e. they are diluted to the same extent or volume would cancel out.

Does diluting a solution change the pH?

Diluting acids and bases

Adding water to an acid or base will change its pH. Water is mostly water molecules so adding water to an acid or base reduces the concentration of ions in the solution. ... The acid is becoming less acidic. Similarly, when an alkali is diluted with water the concentration of OH ^- ions decreases.

What happens when you dilute a buffer solution?

Diluting a buffer solution would decrease its buffer capacity. You can easily notice that the change on the pH is more important when the concentrations of the acid and conjugate base are diluted.