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pH of a Solution given its Composition

Acetic acid (CH3COOH) is a weak acid with the following ionization reaction:

CH3COOH + H2O Û H3O+ + CH3COO- Ka = 1.8 x 10-5

What is the pH of a solution that is 0.5M in acetic acid and 2.5M in sodium acetate, CH3COONa?

Solution Preview

1.8 x 10-5 = [CH3COO-][H3O+]/[CH3COOH]

If XM = amount of acetic acid that dissociates, then X M of H3O+ and CH3COO- ions are formed. The added sodium acetate is a salt containing the cation of a strong base (Na+) and an anion of a weak acid (CH3COO-). This will dissociate completely in water to ...

Solution Summary

This solution provides a calculation of the pH of a solution given its composition.

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