Answer;
548 kJ
Explanation and solution;
The energy in joules of a single photon of wavelength λ in meters is:
E = hc/λ , where h is the planks constant, 6.63x10^-34 J·s, c is the speed of light, 3x10^8 m/s and λ is the wavelength in meters.
= (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.
