Which change leads to a higher concentration of SO₃ in this equilibrium mixture?
2SO₂(g) + O₂(g) ⇌ 2SO₃(g)
ΔH = -188 kJ mol⁻¹
A higher concentration of O₂
B higher temperature
C lower pressure
D use of a catalyst - AQA - A-Level Chemistry - Question 9 - 2019 - Paper 3
Question 9
Which change leads to a higher concentration of SO₃ in this equilibrium mixture?
2SO₂(g) + O₂(g) ⇌ 2SO₃(g)
ΔH = -188 kJ mol⁻¹
A higher concentration of O₂
B ... show full transcript
Worked Solution & Example Answer:Which change leads to a higher concentration of SO₃ in this equilibrium mixture?
2SO₂(g) + O₂(g) ⇌ 2SO₃(g)
ΔH = -188 kJ mol⁻¹
A higher concentration of O₂
B higher temperature
C lower pressure
D use of a catalyst - AQA - A-Level Chemistry - Question 9 - 2019 - Paper 3
Step 1
higher concentration of O₂
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Answer
Increasing the concentration of O₂ will shift the equilibrium position to the right, towards the production of more SO₃. This is in accordance with Le Chatelier's principle, which states that if a change is made to a system at equilibrium, the system will adjust to counteract that change.
Step 2
higher temperature
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Answer
Since the reaction produces SO₃ and is exothermic (ΔH = -188 kJ mol⁻¹), increasing the temperature will shift the equilibrium to the left, reducing the concentration of SO₃.
Step 3
lower pressure
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Answer
Lowering the pressure will shift the equilibrium towards the side with more moles of gas. In this reaction, there are 3 moles of gas on the left (2SO₂ + 1O₂) and 2 moles of gas on the right (2SO₃), so lower pressure would decrease the concentration of SO₃.
Step 4
use of a catalyst
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Answer
The use of a catalyst has no effect on the position of equilibrium; it only accelerates the rate at which equilibrium is reached without changing the concentrations of reactants and products.
