Cambridge IGCSE Chemistry · Syllabus 0620 · Chemical Reactions
Contact Process
What is Contact Process?
The industrial manufacture of sulfur trioxide, used to make sulfuric acid, by the reversible oxidation of sulfur dioxide over a vanadium(V) oxide catalyst. Sulfur dioxide is obtained by burning sulfur or by roasting sulfide ores, oxygen comes from the air, and the reaction is run at about 450 degrees Celsius and only 200 kilopascals, which is 2 atmospheres.
This definition is part of the Chemical Reactions chapter in Cambridge IGCSE Chemistry.
Common mistakes with Contact Process
- 12. “At equilibrium the amounts of reactants and products are equal.” Supplement 6.3.3 Why tempting“Equilibrium” and “balance” suggest equality. RepairThe rates are equal; the concentrations are constant. The Contact process sits at equilibrium with about \(98\%\) product. TransferFill the gap: “the concentrations remain ______.” Constant.
- 17. “The Contact process runs at 200 atmospheres.” Supplement 6.3.10 Why temptingThe two processes share a temperature, so the pressures get shared too. RepairContact runs at \(200\ \mathrm{kPa}\), which is \(2\) atmospheres. Haber runs at \(20\,000\ \mathrm{kPa}\), which is \(200\) atmospheres. Both numbers contain “200”, and the unit is the whole difference. TransferGive both pressures with units, then say why they differ.
Examiner tips on Contact Process
- If you have only one hour before the exam. Every candidate should read the seven danger zones and the nine comparison matrices. A Core candidate should then re-read Figure 6.2, the five factors, and the four colours in Section 6.3A. An Extended candidate should instead re-read the five-line specifications of the Haber and Contact processes and the four oxidation number rules. Those are the densest summaries of the topic for each route: the recall facts, the distinctions that are easiest to merge, and the errors that turn correct chemistry into a wrong answer.