Photoelectric Effect Post-Assessment Questions 29-30

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Samantha Pedersen 2K
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Photoelectric Effect Post-Assessment Questions 29-30

Postby Samantha Pedersen 2K » Mon Oct 05, 2020 1:39 pm

The given information is "Light hits a sodium metal surface and the velocity of the ejected electron is 6.61 x 10^5 m.s-1. The work function for sodium is 150.6 kJ.mol-1"

Question 29) How much energy is required to remove an electron from one sodium atom?

I tried converting the work function from kJ into Joules to get 1.506 x 10^5 Joules, but this was incorrect.

Question 30) What is the frequency of the incident light on the sodium metal surface?

I began this problem by rearranging E = hv to v = E/h to solve for frequency, but because my answer from Question 29 was incorrect, I also got an incorrect answer of 2.27 x 10^38 Hz for this question.

Isabella Chou 1A
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Re: Photoelectric Effect Post-Assessment Questions 29-30

Postby Isabella Chou 1A » Mon Oct 05, 2020 1:59 pm

For number 29, the work function is given in units of kJ/mol. However, since the question is asking for the energy required per sodium atom, you would need to use Avogadro's constant to convert from moles to atoms. After getting this answer, you should get a different answer for number 30 as well. I hope this makes sense!

John Pham 3L
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Re: Photoelectric Effect Post-Assessment Questions 29-30

Postby John Pham 3L » Mon Oct 05, 2020 2:01 pm

For 29, you need to solve per sodium atom. 1.506 * 10^5 is the amount of Joules per mol and you need to divide by Avogadro's constant to convert to Joules per atom. This would give you 2.501 * 10^-19 Joules per Na atom.

You can then plug this in to v = E/h to solve for the frequency of the incident light.


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