Electrolysis

What is an electrolyte?

An ionic compound that is molten or dissolved in water.

What is electrolysis?

The decomposition of an electrolyte using electrical energy from a direct current.

Why must an ionic compound be molten or aqueous for electrolysis?

Its ions must be free to move.

What happens to cations during electrolysis?

They move towards the negatively charged cathode.

What happens to anions during electrolysis?

They move towards the positively charged anode.

What charge does the cathode have during electrolysis?

Negative.

What charge does the anode have during electrolysis?

Positive.

What happens at the cathode?

Reduction occurs.

What happens at the anode?

Oxidation occurs.

What is reduction in terms of electrons?

Gain of electrons.

What is oxidation in terms of electrons?

Loss of electrons.

What is a useful mnemonic for oxidation and reduction?

OIL RIG: Oxidation Is Loss, Reduction Is Gain.

What happens to Cu²⁺ at the cathode?

Cu²⁺ gains electrons to form copper: Cu²⁺ + 2e⁻ → Cu.

What happens to Cl⁻ at the anode?

Chloride loses electrons to form chlorine: 2Cl⁻ → Cl₂ + 2e⁻.

What products form during electrolysis of copper chloride solution?

Copper at the cathode and chlorine at the anode.

What products form during electrolysis of sodium chloride solution?

Hydrogen at the cathode and chlorine at the anode.

What products form during electrolysis of sodium sulfate solution?

Hydrogen at the cathode and oxygen at the anode.

What products form during electrolysis of acidified water?

Hydrogen at the cathode and oxygen at the anode.

What is the volume ratio of hydrogen to oxygen in water electrolysis?

2:1.

What happens during electrolysis of molten lead bromide?

Lead forms at the cathode and bromine forms at the anode.

What products form when a molten binary ionic compound is electrolysed?

The metal forms at the cathode and the non-metal forms at the anode.

What is a half equation?

An equation showing the electron transfer at one electrode.

What must half equations show?

The ions, electrons and products involved.

What is the cathode half equation for copper ions?

Cu²⁺ + 2e⁻ → Cu.

What is the anode half equation for chloride ions?

2Cl⁻ → Cl₂ + 2e⁻.