Which statement about buffer capacity is true?

Which statement about buffer capacity is true?

• A. It remains constant regardless of concentration.
• B. It depends on concentrations and ratio of conjugate components and temperature.
• C. It increases as the ratio deviates from 1:1, and is unchanged by temperature.
• D. It is determined only by the base strength.

Answer: (B)

Buffer capacity is the amount of acid or base a buffer can neutralize before the pH changes appreciably. It depends on how much buffering material you have, which means the total concentrations of the weak acid and its conjugate base, because more material provides more pairs to react with added H+ or OH−. It is strongest when the ratio of the conjugate components is about 1:1, since both forms are present in substantial amounts to absorb added species, keeping the pH near the pKa. If the ratio drifts far from 1:1, the buffer’s ability to counteract additions falls, even if the total amount is the same. Temperature matters because Ka changes with temperature, shifting the pH for a given ratio and altering how effectively the buffer can resist pH changes. So buffer capacity really depends on concentrations, the ratio of the conjugate components, and temperature. The other ideas fail because capacity is not constant with concentration alone, it does not increase by moving away from a 1:1 ratio, and it is not determined solely by base strength.

Buffer capacity is the amount of acid or base a buffer can neutralize before the pH changes appreciably. It depends on how much buffering material you have, which means the total concentrations of the weak acid and its conjugate base, because more material provides more pairs to react with added H+ or OH−. It is strongest when the ratio of the conjugate components is about 1:1, since both forms are present in substantial amounts to absorb added species, keeping the pH near the pKa. If the ratio drifts far from 1:1, the buffer’s ability to counteract additions falls, even if the total amount is the same. Temperature matters because Ka changes with temperature, shifting the pH for a given ratio and altering how effectively the buffer can resist pH changes. So buffer capacity really depends on concentrations, the ratio of the conjugate components, and temperature. The other ideas fail because capacity is not constant with concentration alone, it does not increase by moving away from a 1:1 ratio, and it is not determined solely by base strength.