C4 - Introducing Electrolysis

What is electrolysis?

The breaking down of an ionic compound using electricity.

Why can't solid ionic compounds conduct electricity?

Because the ions are held in a fixed position and cannot move.

Why can molten or dissolved ionic compounds conduct electricity?

Because the ions are free to move and carry charge.

What is an electrolyte?

A liquid or solution that contains free-moving ions and conducts electricity.

What does molten mean?

Melted.

What are the two types of ions in lead bromide (PbBr2)?

Positive lead ions (Pb2+) and negative bromide ions (Br-).

What is the negative electrode called?

The cathode.

What is the positive electrode called?

The anode.

What type of material are electrodes made from?

Conducting material such as graphite or metal.

What happens to positive ions during electrolysis?

They are attracted to the cathode (negative electrode).

What happens to negative ions during electrolysis?

They are attracted to the anode (positive electrode).

What happens to Pb2+ ions at the cathode during electrolysis of lead bromide?

Each Pb2+ ion gains 2 electrons to form a lead atom (reduction).

Is gaining electrons oxidation or reduction?

Reduction.

What happens to Br- ions at the anode during electrolysis of lead bromide?

Each Br- ion loses 1 electron to form a bromine atom (oxidation).

Is losing electrons oxidation or reduction?

Oxidation.

What happens to bromine atoms after electrolysis?

They pair up to form Br2 molecules.

Which phrase helps remember oxidation and reduction in terms of electrons?

OIL RIG (Oxidation Is Loss, Reduction Is Gain).

Why is electrolysis of molten compounds important?

It allows extraction of elements (e.g. metals) from ionic compounds.