CBSE Class 11-science Answered

A buffer solution is a solution comprised of a weak acid and its conjugate base, or a weak base and its conjugate acid. It resists change in the hydrogen ion concentration on the addition of small amount of acid or base.

For ex: If we have a buffer containing an equimolar amount of acetic acid and sodium acetate. The solution will contain large no. of sodium, acetate ions and large no. of undissociated acetic acid molecules.

Now, if a few drops of HCl are added to this solution, the additional H+ ions provided by HCl will combine with the large amount of acetate ions available to form undissociated acetic acid molecules and there will be no change in the pH.