Experiments reveal that O2 undergoes photochemical dissociation into one normal oxygen atom and one oxygen atom, 1.967 eV more energetic than normal. Also, the dissociation of O2  into two normal oxygen atoms needs  498 kJ mol-O2 . Calculate the maximum wavelength effective for the photochemical dissociation of O2 .

eV=1.6×10−19J. Hence:Extra energy for excited oxygen atom=1.967eV×1.6×10−19J1eV=3.15×10−19JBut for normal oxygen atom,E=498×103J1molO2×1molO26.02×1023O2 molecules =8.27×10−19J∴ Total energy for excited oxygen atom=3.15×10−19J+8.27×10−19J=11.42×10−19But, λ=hcEλ=6.626×10−34J.s×3×108ms−11.42×10−19J=1.74×10−7m=1.74×10−7×10−210−2=1.74×100×10−9m=174nm