Buffer pH

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 K_a and pK_a (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.

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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.