Post Module #29 (KJ*mol^-1 problem)

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JennyCKim1J
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Post Module #29 (KJ*mol^-1 problem)

Postby JennyCKim1J » Tue Oct 17, 2017 11:33 am

Light hits a sodium metal surface and the velocity of the ejected electron is 6.61 x 105 m.s-1. The work function for sodium is 150.6 kJ.mol-1.
(From previous Q, Ek = 1.99*10^-19J)

#29. How much energy is required to remove an electron from one sodium atom?
I know this question is just asking for work function. Am I supposed to divide the given value by 6.02214 × 10^23 mol^-1 to get rid of mol^-1?

Annie Lieu-1H
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Re: Post Module #29 (KJ*mol^-1 problem)

Postby Annie Lieu-1H » Tue Oct 17, 2017 11:55 am

Yes, divide the Avogrado's constant in the dimensional analysis so you can convert the energy/sodium mole to energy/sodium atom

Jingyi Li 2C
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Joined: Fri Sep 29, 2017 7:06 am

Re: Post Module #29 (KJ*mol^-1 problem)

Postby Jingyi Li 2C » Wed Oct 18, 2017 9:23 am

You're right. It does ask for the work function. However, the work function it gives you is in KJ.mol-1. So, you have you first multiply it by 10^3 to get J.mol-1. Then, you divide it by Avogadro constant to get J/atom.

104922499 1F
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Joined: Fri Sep 29, 2017 7:04 am

Re: Post Module #29 (KJ*mol^-1 problem)

Postby 104922499 1F » Sat Oct 21, 2017 10:34 pm

yes, divide by Avogadro's constant. Then you can solve the rest of the question

DAllaf
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Re: Post Module #29 (KJ*mol^-1 problem)

Postby DAllaf » Sun Oct 22, 2017 2:36 am

Hi Jenny,

Yes, you should divide by Avogrado's constant (6.02214 x 10^23 mol^-1) so that you can get rid of the mol-1. Then be sure to notice that it gives you kJ, so you need to multiple 150.6 by 10^3, so that you get J only.

Hope this helps


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