A student investigated the effect of the concentration of hydrochloric acid on the rate of reaction between dilute hydrochloric acid and magnesium ribbon.
The length of the magnesium ribbon was kept constant at 3.0 cm.
State one other variable that must be kept constant during this investigation.
87 exam-style questions on Edexcel GCSE Chemistry 8.1 Rates of reaction, covering 8.1.1 Measuring and interpreting rates of reaction, 8.1.2 Collision theory and the factors affecting rate, and 8.1.3 Catalysts and enzymes. Each one has a worked solution and a mark scheme showing where the marks go.