Calculate the amount of water (mL) that needs to be added to 100.0 ml of .53 M acetic acid

Question

to make a solution of pH=3.00

Answer 1

we first find the strength of solution that has a pH= 3,.... H+ = 1e-3

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

1.8 e-5 = [ 1e-3] [ 1e-3] / [HC2H3O2]

[HC2H3O2] = 1e-6 / 1.8e-5

[HC2H3O2] = 0.0555 molar

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now we use the dilution formula:

C1V1 = C2V2

(0.53M) (100.0ml) = (0.0555M) V2

V2 = 954.1 ml

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your answer: you need to add 854.1 ml of water

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