Key Concepts: Rate of reaction = change in amount / time. Factors affecting rate: temperature, concentration, surface area, catalysts. Collision theory explains why reactions occur. Activation energy is minimum energy needed for reaction.
Section A: Measuring Reaction Rates
1. Define rate of reaction. [2]
2. A marble dissolves in acid. 0.8 g dissolves in 20 seconds. [2]
Calculate the rate of reaction
Section B: Factors Affecting Rate
3. State and explain how each factor affects reaction rate: [6]
(a) Temperature increase
(b) Concentration increase
(c) Surface area increase
4. Explain using collision theory why increasing temperature speeds up reactions. [3]
5. Describe an experiment to investigate the effect of surface area using marble chips and hydrochloric acid. [3]
Section C: Catalysts
6. Define a catalyst and explain how it works. [3]
7. Explain why catalysts are chemically unchanged after a reaction. [2]
Total marks: 23
Mark Scheme
1. Measure of how fast a substance is formed or consumed [1]; Usually expressed as amount per unit time [1]
2. Rate = 0.8/20 = 0.04 g/s [2]
3. (a) Rate increases [1]; Particles have more kinetic energy [1]
(b) Rate increases [1]; More particles per unit volume, more collisions [1]
(c) Rate increases [1]; More surface exposed, more collisions [1]
4. Higher temperature means particles move faster [1]; More frequent collisions [1]; More collisions with sufficient activation energy [1]
5. Use different-sized marble chips, keep acid volume/concentration constant, measure gas volume or time to collect fixed volume [3]
6. Catalyst increases rate without being used up; provides lower activation energy pathway [3]
7. Catalyst is not consumed in reaction; remains unchanged at end [2]