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question 27

Posted: Thu Oct 12, 2017 6:32 pm
by Josh Moy 1H
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

Re: question 27

Posted: Thu Oct 12, 2017 7:11 pm
by Miguel Velasco 2J
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).

Re: question 27

Posted: Thu Oct 12, 2017 10:05 pm
by Adrian Franco 3H
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!