A buffer solution is to be made using 1.00 mol dm–3 ethanoic acid, CH3CO2H, and

1.00 mol dm–3 sodium ethanoate, CH3CO2Na.

Calculate to the nearest 1 cm3 the volumes of each solution that would be required to

make 100 cm3 of a buffer solution with pH 5.50.

Clearly show all steps in your working.

Ka (CH3CO2H) = 1.79 × 10–5 mol dm–3

Ok so I used the equation pH=pka+log([base]/[acid])

I got [base]/[acid]=5.66, but I have no idea how to proceed further, since I don't know the number of moles of the ethanoic acid or of sodium ethanoate, however in the answer key they have simply put it like this

B+A=100, B=100-A (B=base, A=acid)

(100-A)/A=5.66 and they got the volume of acid as 15cm^3 and of base 85cm^3.

Can someone please explain?