To draw and explain the shape of graphs of pH against volume of titrant for titrations involving monoprotic acids and bases.

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Problem:

To draw and explain the shape of graphs of pH against volume of titrant for titrations involving monoprotic acids and bases. The combinations we had were: 1) strong acid + strong base (titrant), 2) weak acid + strong base (titrant) and 3) weak base + strong acid (titrant).

Data collection:

Procedure:

We had the different acids and bases in the beaker respectively in the burette and dropped the titrant into the beaker where we had a pH-meter and recorded the result.

  1. We had HCl in a 20 ml beaker and NaOH in a 50 ml burette and a few drops of BTB.
  2. We had HAc in a 20 ml beaker and NaOH in a 50 ml burette and a few drops of BTB.
  3. We had NH3 in a 20 ml beaker and HCl in a 50 ml burette and a few drops of BTB.
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The results were all rather similar; the graph curves were almost the same shape, even though the values differed from the one to another.

*For more information, see attached graphs.

1)        2)        3)

        

Data processing and presentation:

All the results were very much similar – producing very similar graphs. Of course there are uncertainties present. For example it is easy to put in a few drops too much ...

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