CAIE IGCSE Chemistry Sulfur Trioxide Contact Process Conditions

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

Practise recalling the temperature, pressure and catalyst for sulfur trioxide manufacture and writing the balanced reversible Contact process equation.

How this is tested

state about 450 °C, 200 kPa or two atmospheres and vanadium(V) oxide catalyst
write the reversible balanced equation with two sulfur dioxide and oxygen forming two sulfur trioxide
include units and distinguish the Contact process conditions from those used in the Haber process

[Maximum number: 1]

Which row shows the conditions used for the conversion of sulfur dioxide to sulfur trioxide in the Contact process?

pressure / atm

temperature $/{ }^{\circ} \mathrm{C}$

catalyst

250

200

vanadium(V) oxide

450

vanadium(V) oxide

250

200

iron

450

iron

How this is tested

Question 21