Titrations

Making a volumetric solution

1) Weigh required mass of solid into a sample bottle on a 2dp balance.

2) Transfer solid to beaker.

3) Reweigh empty sample bottle.

4) Record the difference in mass between the sample bottle + solid and the empty sample bottle.

5) Add 100cm3 distilled water to beaker. Stir with a glass rod to dissolve solid.

6) Pour solution into a 250cm3 volumetric flask using a funnel.

7) Rinse beaker, funnel and glass rod. Add washings to volumetric flask.

8) Make up to mark with distilled water using a dropping pipette for last few drops.

9) Invert flask several times to ensure uniform concentration.

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Carrying out the titration

1) Rinse each piece of equipment with the solution to be placed in it (and rinse the conical flask with distilled water).

2) Using a volumetric pipette, transfer 25cm3 of the solution of unknown concentration into the conical flask. Touch the surface of the solution with the pipette to add the last drop from the pipette.

3) Add a few drops of suitable indicator to the conical flask.

4) Place a white tile underneath the conical flask to aid observations of colour change.

5) Ensure the jet space of the burette is filled with solution and any air bubbles are removed. Add the solution of known concentration from the burette, swirling the conical flask.

6) When the end point is near, add solution from the burette dropwise.

7) Note the burette reading before and after the addition of the solution of known concentration. Readings should always be to 2dp either ending in 0.00 or 0.05.

8) Repeat the titration until at least 2 concordant results are obtained (within 0.1cm3 of each other).  

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