Fig. 1 shows a student using a respirometer to compare oxygen uptake by germinating pea seeds at 20 °C. A small cap of potassium hydroxide is separated from...
Question 1 Report
Fig. 1 shows a student using a respirometer to compare oxygen uptake by germinating pea seeds at 20 °C. A small cap of potassium hydroxide is separated from the seeds by cotton wool. The chemical absorbs carbon dioxide. A coloured drop in the capillary tube is at the start mark. The student keeps the apparatus in a water bath so that temperature does not change.
(a) Identify the gas absorbed by the potassium hydroxide. [1]
(b) Explain why the coloured drop moves towards the flask while the seeds respire. [2]
Answer Details
(a) Carbon dioxide / CO2 [1] (b) Seeds use oxygen in aerobic respiration [1]; carbon dioxide is absorbed, so gas volume or pressure in the flask decreases and pulls the drop towards it [1]
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