Required Practical: Analysis and purification of water samples
Equipment·
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Method
1 Half fill a beaker with tap water and add some crushed ice to make an ice bath.
2 Put a boiling tube into the ice bath.
3 Add 50 cm3 of solution and a few anti-bumping granules (or broken pottery) into a 100 cm3 Pyrex conical flask.
4 Push a thermometer and an ‘n’ shape delivery tube through two holes in a bung.
5 Put the bung into the conical flask.
6 Adjust the height of the thermometer so that the bulb is in line with the delivery tube.
7 Put the conical flask on top of a tripod and gauze.
8 Put the end of the delivery tube into the test tube in the ice bath.
9 Ignite the Bunsen burner, with the air hole closed onto the safety flame.
10 Open the air hole of the Bunsen burner so the flame turns blue and move the Bunsen burner under the tripod to heat the solution.
11 Note the temperature on the thermometer when it is a constant value. This is the boiling point of the distillate.
12 When a third of a boiling tube of distillate has been collected, remove the delivery tube and then turn off the Bunsen burner.
13 Use a pH probe to test the pH of the distillate.
Evaluate your distillation
What was the substance that makes up the distillate? Hint: use the temperature on the thermometer to suggest the identity of the vapour.�
Outline a method for checking the purity of the distillate.�
Justify when distillation would be an appropriate method for making potable water.�
Explain the difference between simple distillation and fractional distillation.�
Justify why a heating mantle is better than a Bunsen burner in a simple distillation where the distillate is ethanol.
Predict the effect on yield when a condenser rather than a delivery tube and ice bath is used in a distillation setup.