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### Topic: enthalpy and atomic efficiency  (Read 3345 times)

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#### gvsu88

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##### enthalpy and atomic efficiency
« on: December 10, 2011, 09:14:01 PM »
During photosynthesis, plants use energy from sunlight to form glucose (C_6H_12O_6) and oxygen from carbon dioxide and water. Write a balnced equation for photosynthesis and use it to calculate ΔHrxn (report in kJ/mol).

I figured this out, and its 2802.5 kJ/mol

This reaction does not occur spontaneously but requires light to provide the necessary energy. If it requires one photon of 367 nm light to trigger this reaction, what is the atomic efficiency of this reaction (report as a percent).

Atomic efficiency is the percentage of energy used by the reaction compared to the energy absorbed by the system to complete one reaction.

so I used E=hc/wavelength

E = 1.63e-10
but then I don't get the atomic efficiency part. I tried dividing the second number by the first one, then converting to percent but it's wrong, and I have never had to do that before so I don't know what to do. Thanks

#### UG

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##### Re: enthalpy and atomic efficiency
« Reply #1 on: December 11, 2011, 03:17:02 AM »
so I used E=hc/wavelength

E = 1.63e-10
How did you get this? Seems like a huge amount of energy for 1 photon.
Anyway, what about if you had a mole of photons? Wouldn't this result in 1 mole of the reaction?

#### gvsu88

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##### Re: enthalpy and atomic efficiency
« Reply #2 on: December 11, 2011, 12:05:31 PM »
That was exactly what I needed to do! Good call, and thank you!