Chemistry Required Practicals

Question 1

Describe a method to investigate what happens when aqueous solutions are electrolysed using inert electrodes and test a hypothesis?

Answer 1

• Add about 50cm3​ ​of copper chloride solution to a beaker.
• Add the lid and insert electrodes through the holes making sure the electrodes don’t touch.
• Attach crocodile leads to the electrode and connect the rods to the DC terminals of a low voltage power supply.
• Switch the 4V power supply on.
• Turn supply off after a few mins
• Take lit splint to negative electrode, if pop is heard, hydrogen is present, if not, the metal has been formed
• Take glowing splint to the positive electrode to see if it re-ignites and thus indicating oxygen has been formed, if not, the halogen has
• Check hypothesis

Question 2

Describe a method for analysis and purification of water samples from different sources, including pH, dissolved solids and distillation

Answer 2

Part 1: Analyse a sample of water

1. Use universal indicator to test the pH of the water.
2. Measure and record the mass of an empty evaporating basin.
3. Pour 10cm^​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.

Part 2: Purifying water sample by distillation

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.
3. You should observe distilled water being collected after a short while