A buffer is a mixture of which components?

A buffer is a mixture of which components?

• A. A weak acid and its conjugate base
• B. A strong acid and its conjugate base
• C. A weak base and its conjugate acid
• D. A strong acid and a strong base

Answer: (A)

A buffer is made from a weak acid and its conjugate base because this pair can neutralize both added acids and bases, keeping the solution’s pH steady. The weak acid donates protons when a base is added, forming more of its conjugate base, while the conjugate base neutralizes added acid by accepting protons to reform the weak acid. This reversibility is what resists big pH shifts. The relationship pH = pKa + log([conjugate base]/[weak acid]) shows how the ratio controls the pH around the acid’s dissociation constant. When the ratio is near 1, the pH is close to the pKa, giving the strongest buffering effect at that pH. While a buffer can also be formed from a weak base and its conjugate acid, the familiar and commonly taught buffer in many contexts is indeed a weak acid with its conjugate base. Strong acids and their conjugates don’t provide buffering because they dissociate completely and don’t establish the necessary equilibrium.

A buffer is made from a weak acid and its conjugate base because this pair can neutralize both added acids and bases, keeping the solution’s pH steady. The weak acid donates protons when a base is added, forming more of its conjugate base, while the conjugate base neutralizes added acid by accepting protons to reform the weak acid. This reversibility is what resists big pH shifts.

The relationship pH = pKa + log([conjugate base]/[weak acid]) shows how the ratio controls the pH around the acid’s dissociation constant. When the ratio is near 1, the pH is close to the pKa, giving the strongest buffering effect at that pH.

While a buffer can also be formed from a weak base and its conjugate acid, the familiar and commonly taught buffer in many contexts is indeed a weak acid with its conjugate base. Strong acids and their conjugates don’t provide buffering because they dissociate completely and don’t establish the necessary equilibrium.