A student measures the total amount of solute that has diffused through a membrane.
Table
| Time in minutes | Total amount in mg\mathrm{mg}mg |
|---|---|
| 0 | 0 |
| 2 | 16 |
| 4 | 26 |
| 6 | 32 |
Which statement correctly compares the mean rates during the first and last two-minute intervals?
The rate rises from 888 to 16 mg min−116\,\mathrm{mg\,min^{-1}}16mgmin−1, consistent with a larger concentration difference.
The rate falls from 888 to 3 mg min−13\,\mathrm{mg\,min^{-1}}3mgmin−1, consistent with a smaller concentration difference.
The rate falls from 161616 to 6 mg min−16\,\mathrm{mg\,min^{-1}}6mgmin−1, consistent with a smaller concentration difference.
The rate rises from 161616 to 32 mg min−132\,\mathrm{mg\,min^{-1}}32mgmin−1, consistent with a larger concentration difference.
42 exam-style questions on Edexcel GCSE Biology 8.1 Exchange surfaces and diffusion, covering 8.1.1 Introduction to exchange and transport, 8.1.2 Alveoli adapted for gas exchange, 8.1.3 Factors affecting rate of diffusion, and 8.1.4 Rate of diffusion using Fick's law. Each one has a worked solution and a mark scheme showing where the marks go.