In a measurement of the quantum efficiency of photosynthesis in green plants, it was found that 9 qu — Atomic Structure Chemistry Question
Question
In a measurement of the quantum efficiency of photosynthesis in green plants, it was found that 9 quanta of red light at 6900 Å were needed to evolve 1 molecule of O$_2$. The average energy storage in the photosynthesis process is 111.6 kcal/mol of O$_2$ evolved. What is the energy conversion efficiency in this experiment? ($\frac{h \cdot c}{e} = 1.24 \times 10^{-7} \text{ nm·eV}$, 1 eV = 23 kcal/mol)
Answer: D
💡 Solution & Explanation
Energy supplied by 9 quanta $= 9 \times \frac{1240 \text{ eV·nm}}{690 \text{ nm}} = 9 \times 1.797 \text{ eV} = 16.17$ eV. Energy stored per O$_2$ molecule $= \frac{111.6 \text{ kcal/mol}}{23 \text{ kcal/mol/eV}} = 4.85$ eV. Conversion efficiency $= \frac{4.85}{16.17} \times 100 \approx 30\%$. Therefore, correct answer is D.
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