A technician reacts a solid block of iron with dilute hydrochloric acid. The test is repeated with the same mass of iron cut into small identical cubes. All other conditions are kept the same. Which statement about the reaction of the small cubes, compared with the block, is correct?
The iron particles in the cubes are smaller, so they move faster and collide more often
Each collision with the acid has more energy because each cube has a smaller volume
The activation energy is lowered because the iron has been cut into smaller cubes
More iron particles are exposed to the acid, so collisions can happen over a larger area
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.