chemistry topic 4: Chemical Changes, specifically the Electrolysis

Basics of Electrolysis Electrolysis of Molten Ionic Compounds 💧 Electrolysis of Aqueous Solutions Electrolysis of Aluminium Oxide (from Bauxite) Half Equations and Overall Reactions

What is electrolysis?

The breaking down of a compound using electricity.

What type of substance can be electrolysed?

Ionic compounds when molten or dissolved in water (so ions can move)

What happens to positive and negative ions during electrolysis?

What is oxidation and reduction?

What is OIL RIG?

Acronym for Oxidation Is Loss, Reduction Is Gain (of electrons).

What happens during electrolysis of molten ionic compounds (e.g., lead bromide)?

Example: What forms during electrolysis of molten lead bromide (PbBr₂)?

What ions are present in an aqueous solution?

The compound’s ions and hydrogen (H⁺) and hydroxide (OH⁻) ions from water.

At the cathode (−), which ion is discharged?

The least reactive positive ion (usually hydrogen or a metal).

At the anode (+), which ion is discharged?

Example: What happens during electrolysis of sodium chloride solution (brine)?

Why is cryolite used in aluminium extraction?

To lower the melting point of aluminium oxide, reducing energy costs.

What happens at each electrode?

Why must the carbon anodes be replaced regularly?

They react with oxygen to form carbon dioxide (CO₂).

What is a half equation?

An equation showing what happens to one ion at an electrode (gain or loss of electrons).

Example: Electrolysis of lead bromide – write the half equations.