A student investigates how the concentration of hydrochloric acid affects the rate of its reaction with marble chips. The student measures the loss in mass of the flask every 30 seconds.
Which variable must the student keep the same?
The size of the marble chips
The concentration of the acid
The mass lost after 30 seconds
The time taken for the reaction to stop
56 exam-style questions on OCR GCSE Chemistry 5.2 Controlling reactions, covering 5.2.1 Measuring and interpreting rate of reaction, 5.2.2 Factors affecting rate and collision theory, and 5.2.3 Catalysts, activation energy and enzymes. Each one has a worked solution and a mark scheme showing where the marks go.