Chemistry- Electrolysis

year 10 half term 2

Electrolysis

the splitting of ionic substances using electricity

How does electrolysis work?

An electric current is applied to melt the compound, which allows the charged ions to move.

Which metals are extracted using electrolysis?

Metals above carbon

Electrolyte

the liquid or solution that has been broken down by electricity

Electrodes

Solids that are put in the electrolyte that conduct electricity.

Anode

Positively charged electrode

What type of ion always goes to the anode?

non-metals

What do ions do at the anode?

lose electrons

Cathode

Negatively charged electrode

What type of ion always goes to the cathode?

metals

What do ions do at the cathode?

gain electrons

Word equation for the electrolysis of lead bromide

Lead Bromide → lead + bromine

Aqueous Solutions

solutions that have been dissolved in water

What happens at the cathode is the metal is more reactive than hydrogen?

Hydrogen is produced.

What happens at the cathode if the metal is less reactive than hydrogen?

Metal atoms are produced

What happens at the anode if there are halide ions present?

halogen molecules are produced

What happens at the anode if there are no halide ions present?

oxygen is produced

Which type of ions are attracted to the anode and what happens to them there?

OH- ions, which lose electrons to form oxygen molecules.

Reduction

gain of electrons

Oxidation

loss of electrons

What happens when aluminium oxide is extracted from its ore?

It is first dissolved in molten cryolite. The O2- ions are attracted to the anode to form O2 molecules, and the Al3+ ions are attracted to the cathode to form Al ions.

What are electrodes made of?

Graphite

Why are electrodes made of graphite?

Because graphite is a good conductor, unreactive and has a high melting point.

Why must the anode be regularly replaced?

Because it can react with oxygen to form carbon dioxide.

What is the test for carbon dioxide?

Bubbled through limewater in a test tube.

What happens if carbon dioxide is present?

Limewater turns murky

What is the test for hydrogen?

Lit splint held over a test tube

What happens if hydrogen is present?

squeaky pop sound

What is the test for chlorine?

Damp litmus paper held over test tube

What happens if chlorine is present?

Litmus paper turns white

What is the test for oxygen?

Glowing splint held over test tube

What happens if oxygen is present?

Glowing splint relights

How could a sample of gas be collected at the positive electrode?

By putting a tube full of water over the electrode