A-LevelBiologyCell membranes and transport9700/12 · May/June 2025 · Q201 Mark

Some agar was coloured pink using a pH indicator. The pink agar was then used to make three agar cubes with different dimensions. [Figure 20.1 (three agar cubes of dimensions 2x2x2 cm, 4x4x4 cm, 5x5x5 cm)] The cubes were placed in a beaker and covered with 0.1 mol dm⁻³ hydrochloric acid. The temperature of the experiment was standardised at 20 °C. Hydrochloric acid diffused into the agar cubes causing the cubes to become colourless. What is the surface area to volume ratio of the agar cube that became colourless in the least amount of time?

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A0.33:1

B0.83:1

C1.2:1

D3.0:1

✓ Correct answer

D: 3.0:1

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Topic: Cell membranes and transport, A-Level Biology (syllabus 9700). Multiple choice, 1 mark.
Source: A-Level Biology, May/June 2025 Paper 1 Variant 2, question 20.

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