Buffers
What is a buffer?
A buffer is a solution that resists a change in pH. The pH does not drastically change when a small amount of a strong acid or a base is added to the solution. What is a buffer made out of? Buffers consist of large quantities of a weak acid and its conjugate base. A weak acid and its conjugate base and a weak base and its conjugate acid can stay in a solution without neutralizing each other. |
Acidic Buffer Solutions- An acidic buffer has a pH that is lower then 7. An acidic buffer is usually composed of a weak acid and its salt. Example: Ethanoic acid solution and sodium ethanoate solution.
- If the solution has equal molar concentrations of both the acid and the salt, it would have a pH of 4.76. - The pH of a acidic buffer is changed by replacing the acid and its salt. The pH can also be changed by altering that ratio of acid to salt. |
Alkaline buffer solutions- An alkaline buffer has a pH that is higher then 7. A basic buffer is usually composed of a weak base and its salt.
Example: Ammonia solution and ammonium chloride solution. - If these solutions have equal concentrations, then the it's pH would be 9.25. - The pH of a basic buffer is changed by replacing the base and its salt. The pH can also be changed by altering that ratio of base to salt. |
How do buffers work?A buffer is able to resist a change in pH because a buffer contains an equilibrium of large quantities of conjugate acid and the conjugate base of the weak acids and bases present in the solution. So when small amounts of acid of base is added to the buffer solution the buffer is able to resist a change in pH.
How do Calculate a Buffer's Capacity?A buffers capacity means the maximum amount of strong acid or base that can be added to the buffer solution without there being a significant change in pH. The amount of conjugate base present is the maximum amount of acid that can be added to a buffer solution. The amount of conjugate acid present present in the buffer is the maxim amount of base that can be added.
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