A scientist grows a plant with water in which every oxygen atom is the heavy kind, marked ^*O…
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A scientist grows a plant with water in which every oxygen atom is the heavy kind, marked . The carbon dioxide is ordinary. The plant carries out photosynthesis for some hours. Use the equation for molecules of the heavy water. (a) How many heavy oxygen atoms are in the oxygen gas that is released? (b) How many are in the glucose? (c) Where do the oxygen atoms of the new water molecules come from?
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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.
Step 1. The oxygen gas. All water molecules are split. Each gives one oxygen atom, so the gas holds heavy atoms (six molecules of ).
Step 2. The glucose. Glucose gets its six oxygen atoms from carbon dioxide, which is ordinary. It holds heavy atoms.
Step 3. The new water. Six carbon dioxide molecules hold oxygen atoms. Six go into glucose, and six go into the new water molecules. So the new water has ordinary oxygen.
Answer: (a) atoms; (b) atoms; (c) from carbon dioxide.
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