Question

Calculate the pH of the solution produced by adding 10mL of 1M hydrochloric acid to 1L of a solution which is 0.1M acetic acid and 0.1M in sodium acetate (Ka = 1.75 x 10-5 molL-1. Comment on the variation in pH.

Answer 1

A buffer solution is one in which the pH of the solution is "resistant" to small additions of either a strong acid or strong base. Buffers usually consist of a weak acid and its conjugate base, in relatively equal and "large" quantities. Calculations are based on the equation for the ionization of the weak acid in water forming the hydronium ion and the conjugate base of the acid. "HA" represents any weak acid and "A-" represents the conjugate base.

HA(aq) + H2O(l) --> H3O+(aq) + A-(aq)

Ka = [H3O+][A-]