Electrolysis of ionic compounds
Electrolysis is the breaking down or ‘decomposition’ of a substance using
electricity. Ionic substances contain positive ions (cations) and negative ions
(anions) . The ionic substance is melted or dissolved in solution to set the ions
‘free’ to move. The substance being decomposed is called the electrolyte. In
electrolysis the electric current enters and leaves the electrolyte by conducting
rods called electrodes. The positive electrode is called the anode and the
negative electrode is called the cathode. In electrolysis the negative ions move
towards the anode. When they get there they lose electrons to form neutral
atoms. The positive ions move towards the cathode. When they get there they
gain electrons to form neutral atoms.
Challenge: Using the information above to help you match up each keyword to
its definition. Write down the matched entries in your Classwork notebook.
REDOX – reduction and oxidation.
During electrolysis some ions will gain electrons and others will lose electrons.
The process of gaining electrons is called reduction and the ion is said to be
reduced. The process of losing electrons is called oxidation and the ion is said to
be oxidised. To help you remember use this acronym: OIL RIG (Oxidation Is Loss,
Reduction Is Gain).
Complete the following electrode half-equations to show whether the ions will gain
or lose electrons and state whether the ion has been oxidised or reduced.
a) 2Br–  Br2 + ..........e–
b) ..........  Cl2 + 2e–
c) 2O2–  .......... + 4e–
d) Na+ + e–  ..........
e) Ca2+ + ..........  ..........
f) .......... + 2..........  Mg
The electrolysis of copper chloride.
1) Copy the diagram below into your books then label the following:
Cell, Bulb, Anode, Cathode, Molten copper chloride, Chlorine gas,
Copper forming, litmus paper.
2) Draw the ions that would be formed in molten copper chloride
and show which electrode they would move towards.
Answer the following in your Classwork notebook in full sentences.
Post a photograph of your answers in the Google classroom.
3) What is the purpose of electrolysis?
4) Why has a bulb been placed in the circuit?
5) Describe what is happening at the anode and cathode. (Include
half equations in their answers )
6) Suggest why the litmus paper will become bleached.