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Question 2

Sulfur trioxide, an essential intermediate in the manufacturing of sulfuric acid, is produced industrially via the Contact Process. The balanced symbol equation for this equilibrium reaction is:

2SO2(g)+O2(g)⇌2SO3(g) 2\text{SO}_2(\text{g}) + \text{O}_2(\text{g}) \rightleftharpoons 2\text{SO}_3(\text{g}) 2SO2​(g)+O2​(g)⇌2SO3​(g)
a.

The reaction is carried out in a closed system.

State how you can tell from the equation that this reaction is reversible.

[1]
b.

What is meant by the term closed system?

[1]
c.

When dynamic equilibrium is reached, which of these statements are correct?

Select two correct statements:

  • The rate of the forward reaction is equal to the rate of the reverse reaction.
  • The forward and reverse reactions have completely stopped.
  • The concentrations of reactants and products remain constant.
  • The reaction vessel contains only sulfur trioxide.
  • The rate of the forward reaction is greater than the rate of the reverse reaction.
[2]
d.

The equilibrium position can be altered by changing the reaction temperature. Suggest one other change that could be made to the reaction conditions to alter the equilibrium position.

[1]
e.

A chemical plant predicts they will produce 1250 tonnes of sulfur trioxide. They actually produce 925 tonnes of sulfur trioxide. Calculate the percentage yield of sulfur trioxide.

[2]
f.

State why this reaction has an atom economy of 100%. Use the balanced symbol equation.

[1]
Markscheme

Equilibria Questions

  1. GCSE
  2. /Chemistry
  3. /Equilibria

25 exam-style questions on OCR GCSE Chemistry Equilibria. Each one has a worked solution and a mark scheme showing where the marks go.

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