Buffer Calculations
Key Questions
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Buffer solutions are used to calibrate pH meters because they resist changes in pH.
When you use a pH meter to measure pH, you want to be sure that if the meter says pH = 7.00, the pH really is 7.00.
So you use solutions of known pH and adjust the meter to display those values.
Buffers are ideal for this purpose because:
- They are easily prepared for a given pH.
- They are stable for long periods of time.
- They resist changes in pH if you accidentally add a little acid or base or even water.
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A buffer solution will maintain a constant pH with the addition of small amounts of acid and alkali.
There is a limit to the amount of acid or alkali that the buffer can handle.
The buffer capacity is given by the expression:
(dn)/(d(pH))dnd(pH) dndn is a tiny amount of added base which results in tiny change in pH shown asd(pH)d(pH) If you have a weak acid whose dissociation constant is
K_aKa then the buffer capacity is given by :(From Wiki)
C_ACA is the concentration of the acid.