<p>Say you have an acidic solution of 200 ml 1.5 M HCN and you add 100 ml 2 M NaOH. It’s pH is 3.7. (These numbers are made up.) If you add 300 ml of 1 M HCl or 1 M KOH the current solution, the pH will either go up or down. But since it’s a buffers the change won’t be as much as it would’ve been. </p>
<p>(Someone correct me or explain this better if possible.)</p>