Question

What is the longest wavelength of a photon that can cause the dissociation of the O-O bond in ozone ?

Type your answer here: nm

Answer 1

Answer-  Bond is O-O

Longest wavelength required to break this bond = ?

Energy required to break 1 mol of O-O bond is 495 kJ / mol (known value determined experimentally)

so, energy required to break 1 molecule of 0-O bond is 495 kJ /Na(Avogadros no.) i.e

495/ 6.022×10^{+23 =} 82.2 * 10^-23 kJ = 82.2 * 10^-20 J ( 1 kJ = 1000J)

We know that,

E = hc/$\lambda$

where, E = Energy

h = plank's constant = 6.63×10⁻³⁴ m² kg / s

$\lambda$ = wavelength

c = speed of light = 3 * 10⁸ m/s

Put all the values,

E = hc/$\lambda$

82.2 * 10^-20 = (6.63×10⁻³⁴ * 3 * 10⁸ ) / $\lambda$

$\lambda$ = (6.63×10⁻³⁴ * 3 * 10⁸ ) / 82.2 * 10^-20

$\lambda$ = 0.241971 * 10^-6 m = 241.971 * 10^-9 m

1 m = 10^-9 nm

So, 241.971 * 10^-9m will be equal to 241.971 * 10^-9 * 10^-9 nm = 241.97 nm

longest wavelength required to for dissociation is 241.97 nm.