Yeast contains enzymes that convert glucose into ethanol and carbon dioxide. A student investigates the effect of temperature on the rate of this fermentation. She measures the volume of carbon dioxide produced in 10 minutes at different temperatures.
The table shows her results. She did each experiment once.
| Temperature in °C | 15 | 25 | 35 | 45 | 55 |
|---|---|---|---|---|---|
| Volume of carbon dioxide in 10 minutes in cm3\mathrm{cm^{3}}cm3 | 8 | 20 | 38 | 12 | 0 |
Write the word equation for fermentation.
Describe the pattern shown by the results.
Calculate the mean rate of carbon dioxide production at 35 °C, in cm3\mathrm{cm^{3}}cm3 per minute.
At the end of fermentation the mixture contains only a small percentage of ethanol. Name the process used to obtain a more concentrated solution of ethanol from the mixture, and explain how it works.
The student concludes: "The best temperature for the yeast enzymes is exactly 35 °C." Evaluate her conclusion.
54 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.