Answer
239 kJ/mol
Work Step by Step
Energy of one mole of photons = $hν\times\frac{6.022\times10^{23}}{1 mole} = \frac{hc}{λ}\times\frac{6.022\times10^{23}}{1 mole}$
h = $6.626\times10^{-34}Js$
c = $2.997925\times10^{8}ms^{-1}$
λ = 500 nm = $500\times10^{-9}m$
E = $\frac{6.626\times10^{-34}Js\times2.997925\times10^{8}ms^{-1}}{500\times10^{-9}m}\times\frac{6.022\times10^{23}}{1 mole}$ = $2.39\times10^{5} Jmol^{-1}$ = 239 kJ/mol.
