How much energy (in kj) do 3.0 moles of photons, all with a wavelength of 665 nm, contain?

548kj because The energy in joules of a single photon of wavelength λ in meters is:

E = hc/λ

(6.63x10^-34 J·s) (3x10^8 m/s) / (655 nm) (1x10^-9 m/nm) = 3.03x10^-19 J.

The energy in kilojoules of 3 moles of photons of this wavelength is:

(3.03x10^-19 J) (6.02x10^23 / mol) (3.0 mol) / (1000 J/kJ) = 548 kJ