Acid-base equilibria
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I understand how a buffer works with ethanoic acid and sodium ethanoate, when hydrogen and hydroxide ions are added. But if you add sodium ethanoate to it, does the pH of the buffer solution change? All I can think of is you are increasing the concentration of the ethanoate ions.
The equilibrium law shows that the pH of a buffer solution, for a given weak acid and its conjugate base, depends on the ratio of the concentrations of the salt and the unionised acid.
So in the mixture you mention the pH depends on the ratio of the concentration of ethanoate ions and unionised ethanoic acid molecules.
Adding more sodium ethanoate to the buffer solution changes the ratio so the pH of the buffer solution changes.
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updated: 22 June 2004
