Question

The ozone cycle that occurs in the stratosphere is responsible for the absorption of some of the high energy radiation emitted by the sun The photo dissociation of O2(g) is the first step in the ozone cycle. 02(g) + hv → 0(g) + 0(g) The bond dissociation energy of O2 is 495 kJ/mol I. What is the minimum energy a photon could have to be able to break this bond upon absorption? Il. What is the wavelength of the photon? Il. To what region of the electromagnetic spectrum does a photon of this energy belong?

Answer 1

1. energy of the photon should be equal to the bond dissociation energy= 495 kJ/mol

1 mole = 6.022 x 10²³ molecules

energy for breaking one bond = 495000/6.022 x 10²³ = 82198.605 x 10^-23 J

II. Energy of the photon = hc/$\lambda$

h = Planks constant = 6.626 x 10^-34 J.s

Energy = 82198.605 x 10^-23 J

c = 3 x 10⁸m/s

$\lambda$ = wavelength

on substituting values on the above equation

$\lambda$ = 241.69 x 10^-9 m (wavelength of the photon)

III

241.69 nm photon belongs to UV region