Acid - Base Equilibria..........?

Question

A 25.0-ml solution of 0.011M CH3COOH is titrated with 0.200M KOH solution. Calculate the pH after the following additions of the KOH solution:
a) 0.0 ml
b) 5.0 ml

Thank you!

Answer 1

You can't answer this without knowing the Ka value for ethanoic acid, which, if I remember it correctly, is 1.7 x 10-5.

Now the [H+] in the ethanoic acid at the start is given by root Ka x molarity, so you can work this out.

from the figures that you have given, the ethanoic acid is completely swamped by the KOH - work out the moles of each. So the pH of the surplus KOH will have to be worked out by:
1. calculate the total number of moles of CH3COOH
2. calculate the total number of moles of KOH
3. subtract
4. work out the molarity of OH- by realising that the volume is now 30ml.
5. using Kw, work out [H+]
6. calculate the pH