## Post Assessment #28 [ENDORSED]

HanSitoy
Posts: 18
Joined: Fri Sep 29, 2017 7:06 am

### Post Assessment #28

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.
How much energy is required to remove an electron from one sodium atom?

Isn't the energy required to remove the electron equivalent to the work function/threshold energy?

vicenteruelos3
Posts: 42
Joined: Fri Sep 29, 2017 7:07 am

### Re: Post Assessment #28

yes, the energy required to remove an electron is equal to the work function or threshold energy

Christine Wastila 1H
Posts: 61
Joined: Fri Sep 29, 2017 7:04 am

### Re: Post Assessment #28  [ENDORSED]

You need to divide the work function by Avogadro's number (6.022x10^23) because the it was given in kJ/mol and the question asks about the energy needed to remove one electron from ONE sodium atom, not a mole of them. I got confused on that, too! Hope this helps.

Sabrina Dunbar 1I
Posts: 57
Joined: Fri Sep 29, 2017 7:07 am
Been upvoted: 1 time

### Re: Post Assessment #28

Also be aware that the value in in kJ not just J, so you need to also do that conversion

Mishta Stanislaus 1H
Posts: 45
Joined: Fri Sep 29, 2017 7:04 am

### Re: Post Assessment #28

To answer this question you must convert the given work function from kJ to J. Then you must divide by avagadro's number to find the energy required per atom as opposed to per mole.

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