In a 0.738 m solution, a weak acid is 12.5% dissociated. calculate ka of the acid.

Question

Brenton

Chemistry

28 August, 04:25

In a 0.738 m solution, a weak acid is 12.5% dissociated. calculate ka of the acid.

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Answers (1)

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Sly · Answer 1

Answer;

Ka = = 1.153 * 10^-4

Explanation;

Weak acid is HA;

Equilibrium: HA (aq) + H2O (l) H3O^ + (aq) + A^ - (aq)

Ka = [H3O^+][A^-]/[HA]

[H3O^+] = [A^-] = (0.0125) (0.738)

= 0.00923 M and [HA]

= 0.738 M - 0.00923 M = 0.738 M because the value 0.00923 is insignificant in this case.

Ka = (0.00923) ^2 / (0.738)

= 1.153 * 10^-4