STUDENT SPACE · TOPIC 5

Electroplating and aluminium

Apply electrolysis to coating objects and extracting aluminium.

The essentials

The object to be coated is the cathode. Use an electrolyte containing ions of the coating metal.
Bauxite is the principal ore. Purified aluminium oxide is dissolved in molten cryolite for electrolysis.
Cryolite lowers the operating temperature compared with melting pure aluminium oxide.

Try each question before opening its hint or answer. Use paper for calculations and diagrams.

Why must the carbon anodes be replaced during aluminium extraction?

Need a hint for Question 1?

Identify the desired product first, then choose the electrode where its ions gain electrons.

Check Question 1

Oxygen produced at the anodes reacts with carbon to form CO₂, consuming the anodes.

A student connects the object for plating to the positive terminal. Explain the error.

Need a hint for Question 2?

Metal deposition requires reduction on the object.

Check Question 2

The object must be the negative cathode so metal ions gain electrons and coat it.

Explain two reasons why aluminium extraction requires a large energy input.

Need a hint for Question 3?

Consider the electrical process and maintaining a liquid electrolyte.

Check Question 3

Electricity drives electrolysis, and the electrolyte must remain molten. Cryolite reduces the heating requirement.

Use Lesson 5 in your worksheet for written practice. Your teacher will discuss those answers in class.