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Chemical Reactivity · Part 1 of 3
9 exam-style questions with model answers, plus 12 quick multi-choice questions — every question on this part of the standard, grouped by the 3 pages of notes they come from.
Write a full answer before you reveal the model one. That comparison is where the learning happens.
State the three conditions needed for a successful collision between reactant particles.
Define activation energy and explain why a reaction with a high activation energy is slow.
A mixture of methane and oxygen can be kept indefinitely at room temperature without reacting, yet the combustion of methane has ΔrH = −890 kJ mol−1 and once lit continues without further heating. Explain these observations fully.
Name the four factors that affect the rate of a reaction and state the effect of increasing each.
Explain, using collision theory, why powdered calcium carbonate reacts faster with acid than a single large lump of the same mass.
A student claims that increasing the concentration and increasing the temperature both work 'by giving the particles more energy'. Evaluate this claim, explain the actual mechanism of each, and explain why a 10 °C rise typically has a much larger effect on rate than doubling the concentration.
Define a catalyst and state how it increases the rate of a reaction.
Explain, in terms of collision theory, why lowering the activation energy increases the rate of a reaction.
An industrial process uses a catalyst and is run at 450 °C rather than at a higher temperature. Explain the role of the catalyst, why a moderate temperature still gives an acceptable rate, and evaluate the claim that 'using a catalyst is always better than raising the temperature'.