STUDENT SPACE · TOPIC 3

Agents and colour changes

Identify oxidising and reducing agents and interpret colour tests.

The essentials

An oxidising agent oxidises another substance and is itself reduced.
A reducing agent reduces another substance and is itself oxidised.
A reducing agent changes acidified aqueous potassium manganate(VII) from purple to colourless.

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

An oxidising agent is itself oxidised. Correct this statement.

Need a hint for Question 1?

First identify what happens to the substance itself, then name its effect on the other reactant.

Check Question 1

An oxidising agent is itself reduced because it gains electrons.

For CuO + H₂ → Cu + H₂O, identify the oxidising and reducing agents.

Need a hint for Question 2?

Name each substance's own change before identifying its role.

Check Question 2

CuO is the oxidising agent; H₂ is the reducing agent.

A sample turns acidified potassium manganate(VII) colourless. What role does the sample play?

Need a hint for Question 3?

Consider which substance causes the manganate(VII) to gain electrons.

Check Question 3

It acts as a reducing agent; it reduces manganate(VII).

Use Lesson 3 in your worksheet for written practice. Your teacher will discuss those answers in class.