question 27

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Josh Moy 1H
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Joined: Thu Jul 13, 2017 3:00 am

question 27

Postby Josh Moy 1H » Thu Oct 12, 2017 6:32 pm

For question 27, it wants moles of photons, and i found energy to be 4.7x10^-19 J/photon, but when converting to just photons the solution Manual turns the 4.7x10^-19 into photons/J to cancel out jules with the 64J. Why did they do this

Miguel Velasco 2J
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Re: question 27

Postby Miguel Velasco 2J » Thu Oct 12, 2017 7:11 pm

Remember! In E=hv, E is energy PER photon. We have 4.7x10^-19J.photon^-1.
We then multiply 64J (1mole/6.022x10^23J) and get 1.4x10^20 photons (and jewels canceled out).

Adrian Franco 3H
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Re: question 27

Postby Adrian Franco 3H » Thu Oct 12, 2017 10:05 pm

Alternatively, you could also divide to cancel out units:

64 J / [(4.7 x 10^-19) J.photon^-1] = 1.4 x 10^20 photons.

Notice how the joules cancel out!

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