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Chapter 19: Problem 79

Photosynthesis in plants can be represented by the following overall equation: $$ 6 \mathrm{CO}_{2}(g)+6 \mathrm{H}_{2} \mathrm{O}(l) \stackrel{\mathrm{} Light \mathrm{}}{\longrightarrow} C_{6} \mathrm{H}_{12} \mathrm{O}_{6}(s)+6 \mathrm{O}_{2}(g) $$ Algae grown in water containing some $^{18} \mathrm{O}\left(\text { in } \mathrm{H}_{2}^{18} \mathrm{O}\right)$ evolve oxygen gas with the same isotopic composition as the oxygen bin the water. When algae growing in water containing only \(^{18} \mathrm{O}\) were furnished carbon dioxide containing \(^{18} \mathrm{O}\) no \(^{18} \mathrm{O}\) was found to be evolved from the oxygen gas produced. What conclusions about photosynthesis can be drawn from these experiments?

Short Answer

Expert verified
In conclusion, the experiments show that during photosynthesis in plants (algae), the oxygen gas released is derived from water molecules (\(H_2O\)), not from carbon dioxide molecules (\(CO_2\)). This supports the overall photosynthesis equation, indicating that oxygen atoms in the produced oxygen gas come from water, while carbon dioxide molecules contribute to the formation of glucose (\(C_6H_{12}O_6\)).

Step by step solution

01

Experiment 1: Growing algae in water containing some \(^{18}O\) (in \(H_2^{18}O\))

The algae grow in water containing some \(^{18}O\) which is in \(H_2^{18}O\). During the photosynthesis process, the produced oxygen gas has the same isotopic composition as the oxygen in the water. This indicates that the oxygen gas released in the process of photosynthesis comes from the water molecules, not the carbon dioxide molecules.
02

Experiment 2: Growing algae in water containing only \(^{18}O\) and supplying CO₂ containing \(^{18}O\)

In this experiment, the algae grow in water containing \(^{18}O\) and are provided with carbon dioxide that contains \(^{18}O\). However, no \(^{18}O\) was found to be evolved from the oxygen gas produced. This result supports our conclusion from Experiment 1 that the oxygen gas released during photosynthesis comes from the water molecules, not the carbon dioxide molecules.
03

Conclusion from the experiments

Based on the results of both experiments, we can conclude that during photosynthesis in plants (or algae in this case), the oxygen gas released comes from the water molecules (\(H_2O\)) and not from the carbon dioxide molecules (\(CO_2\)). The experiments provide valuable insights into the molecular processes involved in photosynthesis, reinforcing the idea that the oxygen atoms in the produced oxygen gas are derived from water, while the carbon dioxide molecules contribute to the formation of glucose (\(C_6H_{12}O_6\)).

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Most popular questions from this chapter

To determine the \(K_{\mathrm{sp}}\) value of \(\mathrm{Hg}_{2} \mathrm{I}_{2},\) a chemist obtained a solid sample of \(\mathrm{Hg}_{2} \mathrm{I}_{2}\) in which some of the iodine is present as radioactive 131 \(\mathrm{I}\) . The count rate of the \(\mathrm{Hg}_{2} \mathrm{I}_{2}\) sample is \(5.0 \times 10^{11}\) counts per minute per mole of I. An excess amount of $\mathrm{Hg}_{2} \mathrm{I}_{2}(s)$ is placed into some water, and the solid is allowed to come to equilibrium with its respective ions. A \(150.0-\mathrm{mL}\) sample of the saturated solution is withdrawn and the radioactivity measured at 33 counts per minute. From this information, calculate the \(K_{\mathrm{sp}}\) value for \(\mathrm{Hg}_{2} \mathrm{I}_{2}\) $$ \mathrm{Hg}_{2} \mathrm{I}_{2}(s) \rightleftharpoons \mathrm{Hg}_{2}^{2+}(a q)+2 \mathrm{I}^{-}(a q) \qquad K_{\mathrm{sp}}=\left[\mathrm{Hg}_{2}^{2+}\right]\left[\mathrm{I}^{-}\right]^{2} $$

Uranium-2355 undergoes a series of \(\alpha\) -particle and \(\beta\) -particle productions to end up as lead-207. How many \(\alpha\) particles and \(\beta\) particles are produced in the complete decay series?

The most significant source of natural radiation is radon-222. $^{222} \mathrm{Rn},\( a decay product of \)^{238} \mathrm{U},$ is continuously generated in the earth's crust, allowing gaseous Rn to seep into the basements of buildings. Because \(^{222} \mathrm{Rn}\) is an \(\alpha\) -particle producer with a relatively short half-life of 3.82 days, it can cause biological damage when inhaled. a. How many \(\alpha\) particles and \(\beta\) particles are produced when $^{238} \mathrm{U}\( decays to \)^{222} \mathrm{Rn}$ ? What nuclei are produced when \(^{222} \mathrm{Rn}\) decays? b. Radon is a noble gas so one would expect it to pass through the body quickly. Why is there a concern over inhaling \(^{222} \mathrm{Rn}\) ? c. Another problem associated with \(^{222} \mathrm{Rn}\) is that the decay of \(^{222} \mathrm{Rn}\) produces a more potent \(\alpha\) -particle producer $\left(t_{1 / 2}=3.11 \mathrm{min} \text { ) that is a solid. What is the identity of the }\right.$ solid? Give the balanced equation of this species decaying by \(\alpha\) -particle production. Why is the solid a more potent \(\alpha\) -particle producer? d. The U.S. Environmental Protection Agency (EPA) recommends that 222 Rn levels not exceed 4 \(\mathrm{pCi}\) per liter of air $\left(1 \mathrm{Ci}=1 \text { curie }=3.7 \times 10^{10} \text { decay events per second; }\right.$ \(1 \mathrm{pCi}=1 \times 10^{-12} \mathrm{Ci}\) . Convert 4.0 \(\mathrm{pCi}\) per liter of air into concentrations units of \(^{222} \mathrm{Rn}\) atoms per liter of air and moles of \(^{2222} \mathrm{Rn}\) per liter of air.

Explain the difference between somatic damage from radiation and genetic damage. Which type causes immediate damage to the exposed individual?

Zirconium is one of the few metals that retains its structural integrity upon exposure to radiation. The fuel rods in most nuclear reactors therefore are often made of zirconium. Answer the following questions about the redox properties of zirconium based on the half-reaction $$ \mathrm{ZrO}_{2} \cdot \mathrm{H}_{2} \mathrm{O}+\mathrm{H}_{2} \mathrm{O}+4 \mathrm{e}^{-} \longrightarrow \mathrm{Zr}+4 \mathrm{OH}^{-} \quad 8^{\circ}=-2.36 \mathrm{V} $$ a. Is zirconium metal capable of reducing water to form hydrogen gas at standard conditions? b. Write a balanced equation for the reduction of water by zirconium. c. Calculate \(\mathscr{G} \circ, \Delta G^{\circ},\) and \(K\) for the reduction of water by zirconium metal. d. The reduction of water by zirconium occurred during the accidents at Three Mile Island in \(1979 .\) The hydrogen produced was successfully vented and no chemical explosion occurred? If \(1.00 \times 10^{3} \mathrm{kg}\) Zreacts, what mass of \(\mathrm{H}_{2}\) is produced? What volume of \(\mathrm{H}_{2}\) at 1.0 \(\mathrm{atm}\) and \(1000 .^{\circ} \mathrm{C}\) is produced? e. At Chernobyl in \(1986,\) hydrogen was produced by the reaction of superheated steam with the graphite reactor core: $$ \mathrm{C}(s)+\mathrm{H}_{2} \mathrm{O}(g) \longrightarrow \mathrm{CO}(g)+\mathrm{H}_{2}(g) $$ It was not possible to prevent a chemical explosion at Chernobyl. In light of this, do you think it was a correct decision to vent the hydrogen and other radioactive gases into the atmosphere at Three Mile Island? Explain.
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