CAIE IGCSE Chemistry 4.1 Electrolysis

Flashcards about Electrolysis.

Electrolysis

The decomposition of an ionic compound, when molten or in aqueous solution, by an electric current being passed through.

Anode

The positively charged electrode, attracting negatively charged ions towards it.

Cathode

The negatively charged electrode, attracting positively charged ions towards it.

Electrolyte

An ionic compound in the molten or aqueous state that undergoes electrolysis; ions in the electrolyte are able to move freely and are attracted towards the electrode with an opposite charge.

Electrolysis of Molten Lead(II) Bromide

Pb2+ ions are attracted to the cathode, gain electrons and become Pb atoms (lead). Br- ions are attracted to the anode, lose electrons and become Br atoms that pair up to become Br2 molecules (bromine).

Electrolysis of Concentrated Aqueous Sodium Chloride

At the cathode, hydrogen ions gain electrons and produce hydrogen gas (H2(g)). At the anode, chloride ions lose electrons and form chlorine gas (Cl2(g)).

Electrolysis of Dilute Sulfuric Acid

At the cathode, H+ ions gain electrons and become hydrogen gas (H2). At the anode, OH- ions lose electrons and form oxygen gas and water.

Products at the Cathode

Metals or hydrogen are formed. If the metal is more reactive than hydrogen, hydrogen will be produced. If the metal is less reactive than hydrogen, the metal is produced.

Products at the Anode

Non-metals (other than hydrogen) are formed. Oxygen and water are produced unless halide ions are present. If halide ions are present, they lose electrons and form their halogens.

Electroplating

Uses electrolysis to coat a thin layer of a metal onto the surface of another metal to improve appearance and resistance to corrosion.

Electroplating - Cathode

The object that needs electroplating.

Electroplating - Anode

The plating metal (made of the plating metal).

Electroplating - Electrolyte

A solution consisting of ions of the plating metal.

Charge Carriers in Electrolysis - External Circuit

Electrons.

Charge Carriers in Electrolysis - Electrolyte

Ions.

Electrolysis of Aqueous Copper(II) Sulfate (Inert Electrodes)

At the cathode, copper ions gain electrons and become copper atoms, forming a brown copper deposit. At the anode, OH- ions lose electrons and form oxygen gas and water.

Electrolysis of Aqueous Copper(II) Sulfate (Copper Electrodes)

At the cathode, copper ions gain electrons and become copper atoms on the electrode. At the anode, copper from the electrode oxidizes and releases Cu2+ ions into the electrolyte.

Electrolysis of Halide Compound in Aqueous Solution - Anode

Halide ions lose electrons and form their halogens (e.g., chloride ions form chlorine).

Electrolysis of Halide Compound in Aqueous Solution - Cathode

If the metal is more reactive than hydrogen, hydrogen gas is produced. If the metal is less reactive than hydrogen, the metal is produced.

Oxidation Half-Equation

Shows the loss of electrons at the anode (anions lose electrons).

Reduction Half-Equation

Shows the gain of electrons at the cathode (cations gain electrons).

OILRIG

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