Question

Calculate the energy of a photon, in J/mol, having wavelengths of

a) 400 nm and

b) 3.3 micrometers

Answer 1

a)

Apply Rydberg Formula

E = h c / WL

h = Planck Constant = 6.626*10^-34 J s

c = speed of particle (i.e. light) = 3*10^8 m/s

E = energy per particle J/photon

wL = wavleenght in m

E = h c / WL = (6.626*10^-34)(3*10^8) /(400*10^-9) = 4.9695e*10^-19 J/photon

1 mol = 6.022*10^23

then

(4.9695e*10^-19)(6.022*10^23) = 813481.963132 J/mol

b)

if WL = 3.3*10^-6 then

E = h c / WL = (6.626*10^-34)(3*10^8) /(3.3*10^-6) = 6.0236*10^-20 J/photon

E =  6.0236*10^-20 J/photon * 6.022*10^23 photons / mol = 36274.1192 J/mol