Question

Electromagnetic radiation of wavelength 242nm is just sufficient to ionize the sodium atom. Calculate the ionization energy of sodium in kJ /mol.

Answer 1

Given λ = 242 nm

Now,

Energy of 1 photon = hv =hc/λ = (6.63x10^-34 X 3x10⁸) / 242x10^-9

= 8.22x10^-19 J/photon i.e. 8.22x10^-22 kJ/photon

We know that,

Ionization energy of sodium = Energy of one photon of radiation of wavelength

Therefore Ionization energy per mole = 8.22x10^-22 X 6.022x10²³ kJ/mol

= 495 kJ/mol