Core practials

Question 1

How would you set up an experiment for the electrolysis of copper sulphate solution using inert electrodes?

Answer 1

1. [Draw diagram as displayed on pg 139]
   * Anode and cathode in CuSO4 solution.
2. Set up equipment shown as in the diagram above.
3. Turn on the power supply to allow a potential difference to flow through the solution.
4. At the** cathode, copper metal** is produced, since it is less reactive than hydrogen, and coats the electrode.
5. At the anode, oxygen and** water** molecules are produced since there aren’t any halide ions present meaning the OH- molecules are oxidised and loose electrons.

Question 1

How do you set up an experiment for the electrolysis of copper sulphate using non-inert electrodes?

Answer 1

1. [Draw diagram as shown on pg140]
   * Anode an cathode are made from copper and in a CuSO4 solution.
2. Set up equipment as shown in the diagram.
3. Turn on the power supply and allow the potential difference to flow thorugh the solution.
4. The cell should be left for around 30 minutes to ensure a measurable change in mass.
5. The mass of the anode will decrease and the mass of the cathode will increase.
6. This is because copper is transferred from the anode to the cathode.

Question 2

Write a method fot the electrolysis of a molten ionic substance.

Answer 2

1. Put your solid ionic substance in a crucible.
2. Heat the crucible with a Bunsen burner until the solid melts.
3. Once the solid is melted, put two clean, inert electrodes in the electrolyte.
4. Then, connect the electrodes to a power supply using wires and clips.
5. [Draw the diagram on pg141 if you’re feeling like it or they give you space to]

Question 3

Explain how copper is purified using electrolysis.

Answer 3

1. Using two copper electrodes. The anode starts off as a big lump of impure copper, the cathode as a thin sheet of pure copper.
2. Copper ions from the impure anode dissolve in the electrolyte.
3. The copper ions move to the pure copper cathode, and react to form a layer of pure copper.
4. Any impurities from the impure anode sink to the bottom of the cell, forming a sludge.