Why can the buffer solution resist the change of pH caused by external acid and alkali? What are the factors that determine the buffer capacity?

A: The buffer solution can resist the influence of external acids by combining acid-resistant components B- with H+ to form a weak electrolyte HB. When foreign alkali is encountered, H+ in the buffer solution combines with the foreign alkali to form a weak electrolyte, and HB dissociates to supplement the consumed H+. The factors that determine the buffer capacity are: buffer ratio and total concentration.