Required Practical: Analysis and Purification of Water

Aim

To analyse samples of water from different sources by measuring pH and identifying dissolved substances. The samples will then be purified using simple distillation to obtain potable water.

Method

Analysing a sample of water

1. Test the pH of the water sample using universal indicator paper.

2. Weigh and record the mass of an empty evaporating basin to two decimal places.

3. Pour 50 cm³ of the water sample into the evaporating basin.

4. Heat the evaporating basin on a tripod and gauze using a Bunsen burner until all the liquid evaporates.

5. Allow the evaporating basin to cool, then weigh it again.

6. Calculate the mass of dissolved solids remaining in the evaporating basin and record your findings in a table, as shown below:

Water samplepHMass of remaining solid (g)
A21.92
B70.00
C50.1

Purifying a sample of water

1. Pour the water sample into a conical flask and set up the distillation apparatus.

Labelled distillation apparatus for the purification of water.

2. Heat the water using a Bunsen burner until it boils, then reduce the heat to maintain a gentle boil.

3. Collect approximately 20 cm³ of distilled water from the cooled test tube.

4. To determine the boiling point of the distilled water, heat it again. Using a thermometer, observe the temperature at which it boils.

Note: Pure water has a boiling point of 100°C at standard atmospheric pressure. If the distilled water contains impurities, its boiling point might be slightly elevated. Using a thermometer, observe the temperature at which it boils to determine that you’ve produced distilled water.

Results

The distilled water was found to be pure, containing no dissolved solids, and had a pH of 7.

Conclusion

This experiment demonstrates that simple distillation can effectively produce pure water from impure sources, creating potable water for various applications.

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