Redox: oxidation numbers and balancing

Question 1 of 10

What is the oxidation number of Fe in Fe₂O₃?

A. −3 B. +1 C. +4 D. +3

Question 2 of 10

The oxidation number of an uncombined element is

A. +1 B. −1 C. 0 D. equal to its group number

Question 3 of 10

A disproportionation reaction is one in which

A. no electrons are transferred B. the same element is both oxidised and reduced C. two different metals are oxidised D. only oxygen is involved

Question 4 of 10

What is the oxidation number of N in NO₃⁻?

A. −5 B. +3 C. +6 D. +5

Question 5 of 10

Reduction is

A. gain of electrons or decrease in oxidation number B. loss of electrons C. gain of oxygen D. increase in oxidation number

Question 6 of 10

In 2Fe²⁺ + Cl₂ → 2Fe³⁺ + 2Cl⁻, the oxidising agent is

A. Cl₂ B. Fe²⁺ C. Fe³⁺ D. Cl⁻

Question 7 of 10

The rusting of iron is a redox reaction.

A. True B. False

Question 8 of 10

Oxidation and reduction always take place together.

A. True B. False

Question 9 of 10

Acidified potassium dichromate(VI) changes colour from

A. green to orange B. purple to colourless C. yellow to blue D. orange to green when reduced

Question 10 of 10

Hydrogen peroxide can act as both an oxidising and a reducing agent.

A. True B. False

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Questions written by OtisamLMS in the style of the WASSCE. They are not WAEC past questions.

Past questions, worked solutions and curriculum-mapped study material for JHS and SHS students and teachers in Ghana.

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