What are the "Universal" buffer mixtures?

Question

What are the "Universal" buffer mixtures?

1 Answer

Impact of this question

8715 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2015-10-16T00:34:50

Universal buffer mixtures are mixtures of buffers.

Explanation:

No, that's not a facetious answer.

A buffer is a mixture of a weak acid and its conjugate base (or vice versa).

It has its best buffering capacity in the range of $p K_{a} \pm 1$ $"p"K_a±1$ .

If you combine substances with $p K_{a}$ $"p"K_a$ values differing by only 2 $pH$ $"pH"$ units or less, you can prepare a wide range of buffers.

Citric acid is a useful component of a buffer mixture because it has three $p K_{a}$ $"p"K_a$ values (3.13, 4.76, and 6.40), and these are separated by less than two $pH$ $"pH"$ units.

If you add another acid such as $H_{2} {PO}_{4}^{-} / {HPO}_{4}^{-}$ $"H"_2"PO"_4^- //"HPO"_4^-$ ( $p K_{a} = 7.2$ $"p"K_a = 7.2$ ), you can extend the range by another two $pH$ $"pH"$ units.

By adjusting the relative amounts of ${Na}_{2} {HPO}_{4}$ $"Na"_2"HPO"_4$ and citric acid, you can prepare a buffer solution for any $pH$ $"pH"$ between $pH = 3$ $"pH"=3$ and $pH = 8$ $"pH"=8$ .

The mixture is called a universal buffer.

If you add more acids like diethylbarbituric acid ( $p K_{a} = 7.98$ $"p"K_a = 7.98$ ) and boric acid ( $p K_{a} = 9.27$ $"p"K_a = 9.27$ ) and adjust the $pH$ $"pH"$ by adding $NaOH$ $"NaOH"$ , you can prepare a buffer for any $pH$ $"pH"$ in the range from $pH = 2$ $"pH"=2$ to $pH = 12$ $"pH" = 12$ .

Science

Math

Humanities

... and beyond

What are the "Universal" buffer mixtures?

1 Answer

Explanation:

Related questions

Impact of this question