Which statement best describes a buffer's purpose?

Which statement best describes a buffer's purpose?

• A. It neutralizes all acids completely
• B. It stabilizes pH by a weak acid/base pair
• C. It dissolves salts
• D. It increases ionic strength

Answer: (B)

A buffer stabilizes pH by using a weak acid and its conjugate base to neutralize small amounts of added acid or base. When acid is added, the conjugate base component reacts to consume H+ and form the weak acid, preventing a large drop in pH. When base is added, the weak acid donates H+ to neutralize OH−, forming water and more conjugate base, which limits pH rise. This resistance to pH change is crucial in biological systems where enzymes and reactions require a narrow pH range. A buffer won’t neutralize all added acid or completely dissolve salts, nor does it primarily change ionic strength; its role is to keep pH stable around its characteristic pKa.

A buffer stabilizes pH by using a weak acid and its conjugate base to neutralize small amounts of added acid or base. When acid is added, the conjugate base component reacts to consume H+ and form the weak acid, preventing a large drop in pH. When base is added, the weak acid donates H+ to neutralize OH−, forming water and more conjugate base, which limits pH rise. This resistance to pH change is crucial in biological systems where enzymes and reactions require a narrow pH range. A buffer won’t neutralize all added acid or completely dissolve salts, nor does it primarily change ionic strength; its role is to keep pH stable around its characteristic pKa.