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CAIE IGCSE Chemistry Oxygen Gain and Loss in Redox

Practise identifying oxidation as oxygen gain and reduction as oxygen loss by tracking which reactant gains or loses oxygen in a chemical equation.

Syllabus
2026–2028
Course
Chemistry 0620

Exam points

  • define oxidation as gain of oxygen and reduction as loss of oxygen in a reaction
  • track oxygen across an equation to identify which substance is oxidised or reduced
  • recognise roasting or combustion as oxidation and metal-oxide conversion as reduction

6.4.3—Oxidation as gain of oxygen and question 1

[Maximum number: 1]

This question is about nitrogen and some of its compounds.

Some of the ammonia made by the Haber process is converted into nitric acid.

The first stage of this process is the oxidation of ammonia to make nitrogen monoxide.

4NH3( g)+5O2( g)⇌4NO( g)+6H2O( g)4 \mathrm{NH}_{3}(\mathrm{~g})+5 \mathrm{O}_{2}(\mathrm{~g}) \rightleftharpoons 4 \mathrm{NO}(\mathrm{~g})+6 \mathrm{H}_{2} \mathrm{O}(\mathrm{~g})

The process is carried out at 900∘C900^{\circ} \mathrm{C} and a pressure of 5 atmospheres using an alloy of platinum and rhodium as a catalyst.

The forward reaction is exothermic.

State the meaning of the term oxidation.

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