WHAT TO DO TO PASS CHEMISTRY PRACTICAL BASE ON TITRATION BY COOLBOY

Practical activity - carrying out a titration

Titration

There are a number of ways that you could carry out a titration in Chemistry. This is an outline of the required steps to undertake one of these methods.

It is important in this practical to use appropriate apparatus to make and record a range of volume measurements accurately.

Aims

To carry out an accurate titration using dilute hydrochloric acid, dilute sodium hydroxide solution, and phenolphthalein indicator.

Titration is a practical technique used to determine the amount or concentration of a substance in a sample. It is an example of quantitative analysis. An acid-alkali titration can be used to find out what volume of acid (or alkali) of known concentration exactly neutralises a known volume of alkali (or acid) of unknown concentration. This concentration can then be calculated.

To obtain valid results, it is important that measurements are precise and accurate. This can be achieved by using a standard procedure for carrying out a titration.

Method

Use a pipette and pipette filler to add 25 cm3 of alkali solution to a clean conical flask.

Add a few drops of a suitable indicator and put the conical flask on a white tile.

Fill the burette with dilute acid. Flush the tap through to remove any air bubbles. Ensure the burette is vertical.

Slowly add the acid from the burette to the conical flask, swirling to mix. (The mixture may at first change colour, and then back again when swirled.)

Stop adding the acid when the end-point is reached (when the colour first permanently changes). Note the final volume reading.

Repeat steps 1 to 5 until three results are repeatable (in close agreement). Ideally these should lie within 0.10 cm3 of each other.