A leaf fixes 90 millimoles of carbon dioxide in one hour…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A leaf fixes millimoles of carbon dioxide in one hour. One millimole of glucose has a mass of , and one millimole of oxygen gas has a mass of . (a) How many millimoles of glucose are made? (b) What is the mass of the glucose? (c) What mass of oxygen is released?
Need a reminder? The key ideaShow
Priestley (1770): a mint plant restores the air that a burning candle or an animal makes unfit. Ingenhousz (1779): sunlight is needed and only green parts release oxygen. Sachs (1854): glucose is made in green parts and stored as starch. Engelmann: bacteria gather in the blue and red regions of a prism spectrum, the first action spectrum. Van Niel: bacteria using H2S give out sulphur; in green plants the donor is water, so the oxygen comes from water. Overall: . Water is oxidised, carbon dioxide is reduced.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. mmol of .
Plan. Use glucose, and .
Step 1. Glucose. mmol.
Step 2. Its mass. .
Step 3. Oxygen. The leaf releases as many moles of oxygen as the carbon dioxide it fixes, which is mmol. Its mass is .
Check. The oxygen released weighs more than the glucose made. That is right, because six oxygen molecules go with each glucose molecule.
Answer: (a) mmol; (b) mg; (c) mg.
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