pH Titration Curves
- During a titration a pH meter can be used and a pH curve plotted
- A pH curve is a graph showing how the pH of a solution changes as the acid (or base) is added
- The result is characteristically shaped graph which can yield useful information about how the particular acid and alkali react together with stoichiometric information
The features of a pH curve
- All pH curves show an s-shape curve and the midpoint of the inflection is called the equivalence or stochiometric point
- From the curves you can
- Determine the pH of the acid by looking where the curve starts on the y-axis
- Find the pH at the equivalence point
- Find volume of base at the equivalence point
- Obtain the range of pH at the vertical section of the curve
Four types of acid-base titrations
- There are four combinations of acids and alkalis that you should know about:
- strong acid + strong base
- weak acid + strong base
- strong acid + weak base
- weak acid + weak base
pH curves for the four types of acid-base titrations
- Without titles for the graph you can easily recognise which combination is shown by looking at the starting and ending pH and deducing whether the acid and alkali are strong or weak
- Sometimes you may see pH titration curves which show pH plotted against volume of acid added
- This produces the mirror image graph from which you can get all the same information
Comparing different versions of pH titration curves