Question

Calculate the energy in kilocalorie per mol of the photons of an electromagnetic radiation of wavelength $5700\mathring{A}$.

Answer 1

$h\times x=12420eV/A^{\circ }E=\frac{hc}{\lambda }=\frac{12420}{5700}=2.179eV=3.49\times {10}^{-19}JEnergyinJ/mol=E\times N_A=3.49\times {10}^{-19}\times 6.023\times {10}^{23}=21\times {10}^{4}J/mol=210kJ/mol1J=0.239Cal\Rightarrow 1kJ=0.239kCal$

Energy in kCal=$0.239$x$210kCal/mol=50.19kCal/mol$