Chemistry and Chemical Reactivity (9th Edition)

$275.6\ kJ/mol$
$\lambda=434.1\ nm=0.4341\times10^{-6}\ m$ $c=\lambda\times\nu$ $\nu=6.91\times10^{14}\ s^{-1}$ Per photon: $E=h\times\nu$ $E=4.58\times10^{-19}\ J$ Per mole: $4.58\times10^{-19}\ J\times6.022\times10^{23}=275.6\ kJ/mol$