homework problem

Question

The energy required to dislodge electrons from sodium metal via the photoelectric effect is 275 kJ/mol. What wavelength (in nm) of light has sufficient energy per photon to dislodge an electron from the surface of sodium?

Answer 1

I assume you mean 275 kJ/mol of electrons.  Divide 275 kJ by Avogadro's number, 6.02 x 10²³, to get the energy of a single photon that has sufficient energy to eject a single electron.  Suppose the result is E.  Then use

 

E = hc/λ ⇒

 

λ = hc/E

 

h = Planck's constant (look it up)

c = speed of light (look it up)

 

Plug in the numbers in appropriate units and get λ.