Question

)   i. Calculate the Energy of light needed to dissociate the O-O bond in ³O₂ to form ^3pO + ^3pO; (ground state O₂ → O + O)

ii. What is the wavelength of this light in meters or nanometers

iii. What is the closest region of the atmosphere – to earth- that this energy available.

    

Answer 1

(i): Here 3 O2 molecules are dissociated to form 3pO +  3pO.

The bond energy of of O=O molecule is 495 kJ/mol i.e

The bond energy for 1 mole ( = 6.023x10²³ O2 molecules) of O2 = 495 kJ = 495000 J/mol

Hence the bond energy for 3 molecules of O2

= (495000 J/mol) x (1 mol / 6.023x10²³ O2 molecules) x (3 O2 molecules)

= 2.465 x 10^-18 J

Hence the energy of light needed = 2.465 x 10^-18 J (answer)

(ii): E = (h x c / ) = 2.465 x 10^-18 J

=> = (h x c) / 2.465 x 10^-18 J = (6.626 x 10^-34 J.s x 3x10⁸m.s^-1 ) / 2.465 x 10^-18 J = 8.06 x 10^-8 m (answer)

or 0.806 nm

(iii) The closest region of the atmosphere – to earth- that this energy available is ionosphere (answer)