Buffer pH for Acid/Base Solutions

A buffer is a solution that resists a change in pH when either an acid or a base is added. Two species are required in a buffer solution: a weak acid capable of reacting with added OH- ions and a weak base that can consume H3O+ ions. To determine the acidity of the buffer solution, the pH is calculated as the negative of the base-10 logarithm of the hydronium ion concentration. pH values less than 7, exactly 7, and greater than 7 indicate acidic, neutral and basic solutions, respectively.

This module simulates the preparation of a buffer solutions based on three separate weak acid/base conjugate pairs. The constant Ka and pKa (both measures of the acid strength) values for each weak acid are given, and the pH of the solution is calculated upon varying the acid and base concentrations.

INSTRUCTIONS

1. Choose a solution from the menu . (The acid/base conjugate pair is displayed under the Buffer System heading)
2. Vary the concentrations of weak acid and weak base from 0.10 M to 1.0 M using the vertical scroll bars. Observe the calculated pH of the resulting solution.