Electrolysis is the process of using energy supplied by electricity to break ionic compounds back into their component atoms. It is an important process that is used, among other things, for the extraction of reactive metals from their ores, as well as the production of hydrogen and oxygen for use in fuel cells. In this unit you will be studying electrolysis of molten and dissolved ionic compounds. By the end of the unit, you will be able to predict the products of electrolysis of different compounds and explain what is happening in terms of movement of electrons.

Specification links

• Set 1 - Section 4.4.3

• Set 2 & 3 - Section 5.4.3

Task 1b: Listen to the podcast for an overview of this topic:

Task 2b: Make notes that:

• Define electrolysis.

• Draw and label a setup for carrying out electrolysis

• Define the terms electrolyte, cathode, anode

• Explain why electrolysis can only be carried out on ionic compounds that are molten or dissolved in water

Task 3b: Make notes that:

• Describe how metal ions are turned back into atoms.

• Define reduction in terms of electrons

• Describe how non-metal ions are turned back into atoms

• Define oxidation in terms of electrons

Task 3c: Copy and complete this paragraph:

_______________ charged ions are attracted to the cathode.

The ions ________ electrons, turning them back into _______.

The ions are ____________ back into atoms.

Sets 1&2: Task 3d: Copy and complete this table:

Task 4c: Complete and self mark the exam question for your set

Task 5c: Make notes that:

• Describe the extra ions that water provides in a solution of an ionic compound

• Copy and complete these sentences:

In _________ ionic compounds, the only ions present are those in the compound.

In _________ ionic compounds, ___ and ___ ions are present from the water in addition to the ions from the compound.

In solutions, ____________ charged ions are attracted to the cathode. _______ ions come from the salt and ________ ions come from the water.

The ion from the _______ reactive element _______ electrons and so is _________. The other ion stays in solution.

In electrolysis of solutions, ____________ charged anions are attracted to the anode.

If the anion is a ______ (such as chloride, bromide or iodide), they _______ electrons and are ___________ to form a halogen (chlorine, bromine or iodine).

If the anion is anything else (such as _______ or nitrate), the ___________ ions from the water are ________ to form _______.

• Predict the product at the cathode of electrolysis of solutions the following salts. Explain your choices.

1. Sodium chloride

2. Silver (I) nitrate

3. Copper (II) sulfate

4. Iron (III) iodide

Set 1&2 - Write half equations for each reaction

• Predict the product at the anode of electrolysis of solutions the following salts. Explain your choices.

  1. 1. Sodium chloride

     2. Silver (I) nitrate

     3. Copper (II) sulfate

     4. Iron (III) iodide

Set1 & 2 - Write half equations for each reaction

• Explain how electrolysis of sodium chloride solution (brine) can result in three different products

Task 5d: Complete and mark the worksheet

Task 6b: Make notes that:

• Write a method for the electrolysis of solutions

• Predict the products of electrolysis of sodium sulfate and copper chloride

• (Set 1&2) Write half equations for each reaction

Task 6c: Complete and mark the exam questions

Complete the end of unit quiz to make sure you have understood this topic