wavelength and kinetic energy question?

Question

If a minimum of 423.6 kJ/mol is required to remove electrons from C atoms on a surface of a sample of carbon, what is the maximum wavelength (max) of light that can remove an electron from a C atom on this surface?

If the same carbon surface is irradiated with light of =175.7 nm, what is the maximum kinetic energy that a released electron could have?

Answer 1

A wavelength of 175.7nm corresponds to a photon of energy hc/l=6.67x10^-34x3x10^8/(1.757x10^-7)=1.14x10^-18 joules. To remove 1 electron requires 423600 / Avogadro's number=423600/(6.023x10^23)=7.03x10^-19 joule. So you subtract this last figure, the electronic exit work function, from the first figure, the energy of the photon, and what's left is the max. energy the released electron can have.