Concentration & Pressure — Collision Theory Exam
15 Questions · 31 Marks · Sections A, B & C
State the Trend — 1-mark recall questions
The 3-Mark Collision Theory Essay — Paper 4 extended writing
Pressure Specifics — Predict, evaluate, and explain
Section A: The Trend
State the Trend — 1-mark recall questions
State the effect of increasing the concentration of a reactant in solution on the rate of reaction.
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State the effect of increasing gas pressure on the rate of reaction.
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A student doubles the concentration of hydrochloric acid. State the effect this has on the number of particles per unit volume.
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State what happens to the frequency of collisions when the concentration of a solution is increased.
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Magnesium reacts with dilute sulfuric acid. State two ways to increase the rate of this reaction without changing the temperature.
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Section B: The 3-Mark Concentration Essay
The 3-Mark Collision Theory Essay — Paper 4 extended writing
Explain, using collision theory, why increasing the concentration of hydrochloric acid increases the rate of its reaction with calcium carbonate.
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Explain, using collision theory, why increasing the pressure of nitrogen and hydrogen gases increases the rate of the Haber Process reaction.
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A student adds excess zinc to 50 cm³ of 0.5 mol/dm³ hydrochloric acid. She then repeats the experiment using 50 cm³ of 1.0 mol/dm³ hydrochloric acid. Explain, using collision theory, why the second experiment produces hydrogen gas faster.
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Explain, using collision theory, why a reaction between two gases occurs faster at higher pressure.
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The graph shows that a more concentrated acid produces hydrogen faster at the start but both experiments produce the same total volume of gas. Explain both observations.
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Section C: Pressure Specifics
Pressure Specifics — Predict, evaluate, and explain
Explain why increasing pressure has NO effect on the rate of a reaction between two solid powders.
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A student claims that increasing pressure will speed up the reaction between sodium chloride solution and silver nitrate solution. Evaluate this claim.
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State why changing pressure is a useful variable in the Haber Process but not in the reaction between iron and dilute sulfuric acid.
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The Contact Process produces sulfur trioxide: 2SO₂(g) + O₂(g) ⇌ 2SO₃(g). Explain, using collision theory, why increasing the pressure increases the rate of the forward reaction.
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A chemist wants to increase the rate of the reaction: C(s) + O₂(g) → CO₂(g). She considers increasing the pressure. Predict and explain whether this would be effective.
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