CAIE IGCSE Chemistry 6.3.9 Sources of the sulfur dioxide (burning

Cambridge IGCSE Chemistry 0620 syllabus for exams in 2026, 2027 and 20282026–2028

Practise stating how Contact process reactants are obtained, from burning sulfur, roasting sulfide ores and using oxygen from air.

How this is tested

describe sulfur dioxide production by burning sulfur in air or roasting sulfide ores
use zinc blende as a sulfide ore example and name sulfur dioxide as a roasting product
state air as the oxygen source for the Contact process when raw materials are tested

[Maximum number: 2]

Over 200 million tonnes of sulfuric acid are manufactured every year.

Part of the manufacture of sulfuric acid involves converting sulfur dioxide to sulfur trioxide.

Describe two methods by which sulfur dioxide is obtained.

1
2

The conversion of sulfur dioxide to sulfur trioxide is a reversible reaction which can reach equilibrium.

2 \mathrm{SO}_{2}(\mathrm{~g})+\mathrm{O}_{2}(\mathrm{~g}) \rightleftharpoons 2 \mathrm{SO}_{3}(\mathrm{~g})

How this is tested

Question 3(b)(i)