Question

The work function of an element is the energy required to remove an electron from the surface of the solid. The work function for rubidium is 218.1 kJ/mol (that is, it takes 218.1 kJ of energy to remove 1 mole of electrons from 1 mole of Rb atoms on the surface of Rb metal). What is the maximum wavelength of light that can remove an electron from an atom in rubidium metal?

Answer 1

Answer:

λ = 548.7 nm

Explanation:

Hi!

First we want to know how much energy we need to remove 1 electron from the surface of the solid:

218.1 kJ/mol => 218 100 J / (6.022 x 10^23) electrons

                             = 3.621 x 10^-19 J/electron  

That is we need 3.621 x 10^-19 J to remove one electron

Now we can calculate the wavelength that a photon must have in order to have this energy:

E = (hc) / λ

λ = (hc) / Ε

where

 h = 6,626070150(69) ×10 -34 Js (wikipedia)

 c = 3 x10^8 m/s

hc = 1.987 x 10^-25 Jm

Therefore:

λ = ( 1.987 x 10^-25 /3.621 x 10^-19 ) m = 5.487 x 10^-7 m

λ = 548.7 nm