RP8: Water Purification

Question 1

What is the aim of this experiment?

Answer 1

• Analysis and purification o f water samples from different sources.
• To include pH measurement, removal of dissolved solids and distillation.

Question 2

How would you analyse a sample of water?

Answer 2

1. Use universal indicator to test the pH of the water.
2. Measure and record the mass of an empty evaporating basin.
3. Pour 10 cm​3​ water into the evaporating basin and evaporate the water using a
   bunsen burner until the most of the water has evaporated.
4. Once the evaporating basin is cool, reweigh and record the change in mass. 5. Calculate the mass of dissolved solids in the water.

Question 3

How would you purify a sample of water by distillation?

Answer 3

1. Place the water sample in a conical flask and set up the apparatus for distillation.
2. Heat the water gently using a bunsen burner until it boils. Then reduce the heat so the
   water boils gently.
3. Collect around 1 cm depth of water in the cooled test tube, then stop turn the bunsen
   burner off.
4. Analyse the water you have distilled with cobalt chloride paper.

Question 4

List some safety precautions

Answer 4

• Do not ingest the water
• Bunsen burner turned off or put on safety flame when not in use
• Hair tied back

Question 5

How can you test the pH of a sample of water?

Answer 5

• DIgital pH próbę or universal indicator

Question 6

How could you find the mass of salt dissolved in a sample of water?

Answer 6

• Weigh an empty evaporating basin
• Fill with a sample of water and heat until water evaporates
• Reweigh salts left in basin and calc mass of solids that were dissolved in the sample

Question 7

How could you test that the water collected form a distillation experiment is pure water?

Answer 7

• Check the pH is still pH 7
• Determine the boiling point and check it matches that of water (100C)