Improving processes and products

What is electrolysis?

The decomposition of an ionic compound using electricity.

Why must an electrolyte be molten or dissolved?

So ions are free to move and carry charge.

What is an electrolyte?

A substance that conducts electricity when molten or in solution.

What is the cathode?

The negative electrode.

What is the anode?

The positive electrode.

What happens at the cathode?

Reduction (gain of electrons).

What happens at the anode?

Oxidation (loss of electrons).

Which ions go to the cathode?

Positive ions (cations).

Which ions go to the anode?

Negative ions (anions).

What happens at the cathode in aqueous solutions?

The least reactive metal or hydrogen is discharged.

What happens at the anode in aqueous solutions?

Halide ions are discharged, otherwise oxygen forms.

Why can hydrogen be produced in electrolysis?

Water provides H⁺ ions.

What is extraction?

Removing a metal from its ore.

How are metals less reactive than carbon extracted?

Reduction using carbon.

How are metals more reactive than carbon extracted?

Electrolysis.

Why is electrolysis expensive?

It uses large amounts of electricity.

What ore is aluminium extracted from?

Bauxite.

Why is cryolite used in aluminium extraction?

To lower the melting point and reduce energy use.

What happens at the cathode in aluminium extraction?

Aluminium ions gain electrons to form aluminium metal.

What happens at the anode in aluminium extraction?

Oxygen forms and reacts with carbon to produce CO₂.

Why do anodes need replacing in aluminium extraction?

They react with oxygen and wear away.

What is a fuel cell?

A device that produces electricity from chemical reactions.

What fuels are used in hydrogen fuel cells?

Hydrogen and oxygen.

What is the only waste product of hydrogen fuel cells?

Water.

What is an advantage of hydrogen fuel cells?

No carbon dioxide is produced.

What is a disadvantage of hydrogen fuel cells?

Hydrogen is difficult to store and transport.

What is corrosion?

The destruction of metals by reactions with the environment.

What is rusting?

Corrosion of iron in the presence of oxygen and water.

What conditions are needed for rusting?

Oxygen and water.

How can rusting be prevented?

Painting, oiling or galvanising.

What is galvanising?

Coating iron with zinc.

Why does zinc protect iron?

Zinc is more reactive and corrodes instead.

What is a displacement reaction?

A more reactive metal displaces a less reactive metal.

What determines if displacement occurs?

The reactivity series.

Example of displacement reaction

Iron + copper sulfate → iron sulfate + copper.

Why is recycling metals important?

It conserves resources and reduces environmental damage.

Why does recycling save energy?

Less energy is needed than extracting metals from ores.

Environmental benefit of recycling

Reduces mining and pollution.

What is bioleaching?

Using bacteria to extract metals from low-grade ores.

How do bacteria extract metals in bioleaching?

They produce substances that dissolve the metal compounds.

Advantage of bioleaching

Uses less energy than traditional extraction.

Disadvantage of bioleaching

It is slow.

What is phytoextraction?

Using plants to absorb metal compounds from the soil.

How are metals obtained in phytoextraction?

Plants are burned and metals are collected from the ash.

Advantage of phytoextraction

Low cost and less environmental damage.

Disadvantage of phytoextraction

Slow process and low yield.

Why do ionic compounds conduct electricity?

They have mobile charged ions.

Why does electrolysis require energy?

Energy is needed to break ionic bonds.

Why does reactivity affect discharge?

Less reactive elements gain electrons more easily.