Which statement best describes the effect of temperature on buffers as described in the material?

Which statement best describes the effect of temperature on buffers as described in the material?

• A. The pH of the buffer can drift because Ka and Kb change with temperature.
• B. Temperature has no effect on buffering.
• C. Only pH of the buffer remains exactly constant.
• D. All buffers become stronger as temperature rises.

Answer: (A)

Temperature influences buffering because the equilibria of acid–base reactions depend on temperature, so the dissociation constants Ka and Kb change as temperature changes. In a buffer, the pH is set by the balance between the weak acid and its conjugate base, described by pH = pKa + log([A-]/[HA]), and pKa = -log Ka. When temperature shifts Ka, the pKa shifts too, which moves the point at which the buffer resists pH changes. So even with fixed amounts of acid and base, the pH can drift with temperature. The other statements don’t fit because buffering is not completely immune to temperature changes, and buffers don’t automatically become stronger with higher temperature. The key idea is that pH can drift as temperature alters Ka and Kb, which changes the position of the buffer’s equilibrium.

Temperature influences buffering because the equilibria of acid–base reactions depend on temperature, so the dissociation constants Ka and Kb change as temperature changes. In a buffer, the pH is set by the balance between the weak acid and its conjugate base, described by pH = pKa + log([A-]/[HA]), and pKa = -log Ka. When temperature shifts Ka, the pKa shifts too, which moves the point at which the buffer resists pH changes. So even with fixed amounts of acid and base, the pH can drift with temperature.

The other statements don’t fit because buffering is not completely immune to temperature changes, and buffers don’t automatically become stronger with higher temperature. The key idea is that pH can drift as temperature alters Ka and Kb, which changes the position of the buffer’s equilibrium.