Question

In: Chemistry

For a 0.100 M solution of K2HPO4, find each of the following values: pH, [H+], [HPO42-],...

For a 0.100 M solution of K2HPO4, find each of the following values: pH, [H+], [HPO42-], [PO43-], and [H2PO4-]. Use the minimum number of approximations.

Expert Solution

HPO42- -------------> H+ + PO43-

0.100 0 0

0.100-x x x

Ka3 = x^2 / 0.100 - x

4.8×10^–13 = x^2 / 0.100 - x

x = 2.19 x 10^-7

[H+] = 2.19 x 10^-7 M

pH = -log (2.19 x 10^-7)

pH = 6.66

[H+] = 2.19 x 10^-7 M

[HPO42-] = 0.100 M

[PO43-] = 2.19 x 10^-7 M

HPO42- + H2O --------------> H2PO4- + OH-

0.100 0 0

0.100 - x x x

Kb = x^2 / 0.100 - x

1.61 x 10^-7 = x^2 / 0.100 - x

x = 1.27 x 10^-4

[H2PO4-] = 1.27 x 10^-4 M

queen_honey_blossom answered 3 years ago

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