In an investigation, unsaturated oil reacts with hydrogen for 40 s. Nickel is present in some runs and absent in others. Each run uses 25 cm3 of oil at the same temperature. The decrease in the volume of hydrogen is measured.
What is the dependent variable?
Whether the nickel catalyst is present
The 25 cm325\,\mathrm{cm^3}25cm3 volume of oil used
The decrease in the volume of hydrogen after 40 s40\,\mathrm{s}40s
The fixed reaction time of 40 s40\,\mathrm{s}40s
122 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.