For the mathematicians - The origin of rapid pH change - Ignore this if you don't like it

• Imagine a strong alkali being added to a strong acid.

• Lets look at the pH of the solution 1 drop before and 1 drop after the equivalence point:

• Assume that 1 drop has a volume of 0.05cm³

• Also that 1 drop does not appreciably change the total volume at neutralisation.  Total volume = 50cm³

1 drop before = acidic

• Calculate the pH of the solution 1 drop before neutralisation.

1 drop after = alkali

• Calculate the pH of the solution 1 drop after neutralisation.

See your chemistry teacher if you require help in this calculation