What are some common buffers used in chemistry problems and how do they help maintain a stable pH level?

Common buffers used in chemistry problems include acetic acid/sodium acetate, phosphate buffer, and Tris buffer. Buffers help maintain a stable pH level by resisting changes in pH when small amounts of acid or base are added. This is achieved through the presence of a weak acid and its conjugate base in the buffer solution, which can react with added acid or base to minimize pH changes.