A pad of steel wool and a solid steel block of the same mass are left outside in the same damp conditions. Why does the steel block rust more slowly than the steel wool?
The block's particles are packed more tightly, so collisions between the reactants occur less often.
The block causes more collisions to be unsuccessful, so fewer collisions produce a reaction.
The block contains fewer iron particles, so collisions between the reactants occur less often.
Less of the steel is exposed to the air and water, so collisions between the reactants occur less often.
127 exam-style questions on AQA GCSE Chemistry 6.1 Rate of reaction, covering 6.1.1a Calculating rates of reactions, 6.1.1b Gradient of a tangent as rate, 6.1.2 Factors which affect the rates of chemical reactions, 6.1.3 Collision theory and activation energy, and 6.1.4 Catalysts. Each one has a worked solution and a mark scheme showing where the marks go.