MCQ Detailed View

A buffer is a substance or solution that resists a significant change in pH when small amounts of an acid or a base are added. It works by neutralizing added hydrogen ions (H⁺) or hydroxide ions (OH⁻), thereby keeping the pH nearly constant. Buffers are important in both laboratory experiments and biological systems, where maintaining a stable pH is necessary for proper reactions and processes.

A buffer solution is usually made of a weak acid and its conjugate base or a weak base and its conjugate acid. For example, acetic acid and sodium acetate form a common buffer system. The weak acid reacts with added bases, while the conjugate base reacts with added acids. This dual action helps stabilize the pH.

In contrast, neutralization refers to a chemical reaction between an acid and a base that produces salt and water. Neutralization does not maintain pH balance; instead, it changes the pH toward neutrality. Osmosis is the movement of solvent molecules across a semipermeable membrane and has no relation to pH control. Active transport is a biological process where molecules move across membranes using energy, also unrelated to pH balance.

Buffers are essential in analytical chemistry because many chemical reactions, titrations, and measurements depend on stable pH conditions. For example, in acid-base titrations, buffers help maintain accuracy by minimizing sudden pH shifts. In biological systems, buffers such as the bicarbonate buffer in human blood are vital for maintaining pH around 7.4, which is necessary for enzyme activity and cell survival.

The concept of buffer capacity is also important. It refers to how much acid or base a buffer can neutralize before a significant pH change occurs. Stronger buffer systems have higher buffer capacity and can resist greater changes.