Question

1 m acetic acid solution is titrated against 0.1 m naoh solution

Answer 1

Answer:

We have to start with the equation for weak acids

Kz(HAc) = [H3O+]*[Ac-]/[HAc]

At 1/4 and 3/4 stage we have an acetate buffer. With the buffer approximation we don’t need the volume and use the ratio Ac- : HAc

At stage 1/4 [Ac-] : [HAc] = 1 : 3

At stage 3/4 [Ac-] : [HAc] = 3 : 1

From the first formule we can derive pH = pKz - log [HAc]/[Ac-]

pH(1/4) = 4.77 -log (3/1) and pH(3/4) = 4.77 - log(1/3)

So the difference in pH = 2*log(3) = 0.95