During a colour-change reaction, a stop clock is stopped when the mixture reaches a reference shade. At 50 ∘C50\,^\circ\mathrm{C}50∘C, the reference shade is reached after 9 s.
For this reaction, the rate at any temperature is twice its value 10 ∘C10\,^\circ\mathrm{C}10∘C lower.
How long should the reaction take to reach the reference shade at 20 ∘C20\,^\circ\mathrm{C}20∘C?
54 s
27 s
18 s
72 s
122 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.