Rates of Chemical Reaction
Chemistry · 50 practice questions
Factors that change reaction rate — temperature (e.g. HCl + Na₂S₂O₃, Mg + HCl), concentration/pressure, surface area (e.g. powdered vs. lump marble with HCl), catalyst (e.g. decomposition of H₂O₂ or KClO₃ with/without MnO₂); reaction rate curves; activation energy — Arrhenius' law, collision theory, and the effect of light on reactions (e.g. halogenation of alkanes).
- Identify the factors that affect the rate of a chemical reaction.
- Determine the effects of temperature, concentration/pressure, surface area and catalysts on reaction rate.
- Interpret reaction rate curves and solve simple problems on reaction rates.
- Relate reaction rate to the kinetic theory of matter.
- Examine the significance of activation energy and deduce it from reaction rate curves.
Try a few questions
- Practice question 1
The rate of a chemical reaction is generally defined as the
- A.total amount of reactant present at the very start of the reaction
- B.change in concentration of a reactant or product per unit time
- C.total amount of product present at the very end of the reaction
- D.time taken for the reactants to be mixed together initially
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B. change in concentration of a reactant or product per unit time
Rate specifically measures how quickly concentration is changing as the reaction proceeds.
- Practice question 2
A graph plotting reaction rate against temperature typically shows the rate
- A.decreasing steadily as temperature rises
- B.increasing, often quite steeply, as temperature rises
- C.remaining completely flat regardless of temperature
- D.increasing only up to a fixed maximum temperature and then dropping to zero instantly
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B. increasing, often quite steeply, as temperature rises
Higher temperatures generally accelerate reaction rates, often quite sharply, as shown on such a graph.
- Practice question 3
A heterogeneous catalyst, unlike a homogeneous one, exists
- A.in the same physical phase as the reactants at all times
- B.in a different physical phase from the reactants, such as a solid catalyst used with gaseous reactants
- C.only ever in the liquid phase, regardless of the reactants
- D.in no defined physical phase at all
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B. in a different physical phase from the reactants, such as a solid catalyst used with gaseous reactants
Heterogeneous catalysis is defined by the catalyst occupying a separate phase from the reacting substances.
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