How much 0.1M sodium acetate (ml) should be added to 100.0 ml of 0.53M acetic acid to make a solution's pH=3?

Question

How much 0.1M sodium acetate (ml) should be added to 100.0 ml of 0.53M acetic acid to make a solution's pH=3?

Answer 1

HC2H3O2 --> H+  & C2H3O2-

K = [H+] [C2H3O2-] / [HC2H3O2]

1.8e-5 =  [1e-3] [C2H3O2-] / [0.53]

[C2H3O2-]  = 9.54e-3 molar acetate

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find the moles of acetate needed to be in  the 100ml  of solution:

0.100 litres @ 9.54e-3 mol/litre = 9.54e-4 moles of acetate

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find the volume  of 0.1 molar sodium acetate that will provide those moles of acetate:

9.54e-4 moles @ 0.1 mol/litre = 9.54 e-3 litres = 9.5  ml

your answer is: 9.5 ml of sodium acetate solution needs to be added

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this will dilute both the sodium acetate & the acetic acid upon mixing, but it won't matter ,... the pH will still be 3