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

JennyCKim1J
Posts: 51
Joined: Fri Sep 29, 2017 7:04 am

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

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
Posts: 68
Joined: Fri Sep 29, 2017 7:04 am
Been upvoted: 1 time

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

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
Posts: 56
Joined: Fri Sep 29, 2017 7:06 am

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

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
Posts: 53
Joined: Fri Sep 29, 2017 7:04 am

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

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

DAllaf
Posts: 20
Joined: Fri Sep 29, 2017 7:04 am

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

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