Titration and pH
Add alkali to acid drop by drop and watch the pH curve and indicator colour change.
- Neutralisation
- pH scale
- Titration curves
Alkali added
0.0cm³
pH
1.00
Equivalence at
25cm³
Solution is
acidic
Predict
What is the pH at the equivalence point of a strong acid–strong alkali titration?
Experiment
- 1Run a strong-acid titration and read the pH at 25 cm³.
- 2Switch to a weak acid and compare both the starting pH and the pH at equivalence.
- 3Find how many cm³ it takes for the pH to travel from 4 to 10.
Explain
Neutralisation is H⁺(aq) + OH⁻(aq) → H₂O(l). As alkali is added, H⁺ ions are removed and the pH climbs — slowly at first, because plenty of acid remains.
Near the equivalence point almost no H⁺ is left, so each further drop causes a large change: the near-vertical section of the curve.
A strong acid is fully dissociated, so it starts at a much lower pH than a weak acid of the same concentration. That is a difference in dissociation, not in concentration — a distinction exam questions test constantly.