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Question #9732f

1 Answer

May 20, 2017

You can't do it.

Explanation:

To make a buffer with pH = 9, you need an acid with $p K_{a} = 9 \pm 1$ $"p"K_text(a) = 9 ± 1$ .

Citric acid is a tribasic acid with the formula $C_{6} H_{8} O_{7}$ $"C"_6"H"_8"O"_7$ or $H_{3} C_{6} H_{5} O_{7}$ $"H"_3"C"_6"H"_5"O"_7$ .

The weakest form of the acid, ${HC}_{6} H_{5} O_{7}^{2-}$ $"HC"_6"H"_5"O"_7^"2-"$ has a $p K_{a}$ $"p"K_text(a)$ of only 6.40.

Thus, you can't use it to make a buffer with pH = 9.

However, it would be great for making a buffer with pH = 7.

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