Problem: A buffer solution contains 0.323 M KHSO3, and 0.257 M K2SO3.If 0.0495 moles of sodium hydroxide are added to 250. mL of this buffer, what is the pH of the resulting solution?(Assume that the volume does not change upon adding sodium hydroxide)pH =

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FREE Expert Solution

The buffer solution is composed of KHSO3 and K2SO3. These two components will break up in the solution:

KHSO3(aq)  K+(aq) + HSO3-(aq)

K2SO3(aq)  2 K+(aq) + SO32-(aq)


HSO3-is a weak acid and based on the Bronsted-Lowry definition, an acid is a proton (H+). Once HSO3- loses its proton, its conjugate base is formed:

HSO3-(aq)  +   H­2O(l)  →   SO32-­(aq)   +   H3O+(aq)
(weak acid)    (base)     (conjugate base)    (conjugate acid)

Whenever we have a conjugate base and a weak acid, we have a buffer.

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Problem Details

A buffer solution contains 0.323 M KHSO3, and 0.257 M K2SO3.

If 0.0495 moles of sodium hydroxide are added to 250. mL of this buffer, what is the pH of the resulting solution?
(Assume that the volume does not change upon adding sodium hydroxide)

pH =



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