Question

An important reaction in the formation of photochemical smog is the photodissociation of NO2: NO2 + hv >>> NO(g) + O(g) The maximum wavelength of light that can cause this reaction is 420 nm. a) In what part of the electromagnetic spectrum is light with this wavelength found? b) What is the maximum strength of a bond, in kJ/mol, that can be broken by absorption of a photon of 420-nm light? c) Write out the photodissociation reaction showing Lewis-dot structures.

Answer 1

Explanation:

$NO_2 + hv\rightarrow NO(g) + O(g)$

The maximum wavelength of light that can cause this reaction is 420 nm.

a) The wavelength given lies in the range of visible light range that is from 400 nano meters to 700 nano meters.

The light with wavelength of 420 nm is found in the range of visible light.

b)The maximum strength of a bond :

$E=\frac{h\times c}{\lambda}$

where,

E = energy of photon = Energy required to break single molecule of nitrogen dioxide

h = Planck's constant = $6.626\times 10^{-34}Js$

c = speed of light = $3\times 10^8m/s$

$\lambda$ = wavelength = $420 nm=420\times 10^{-9}m$

$E=\frac{6.626\times 10^{-34}Js\times 3\times 10^8 m/s}{420\times 10^{-9}m}$

$E=4.733\times 10^{-19} J$

Energy required to break 1 mole of nitrogen dioxide molecules:

$= E\times N_A=4.733\times 10^{-19} J\times 6.022\times 10^{23} mol^{-1}$

$=285,012.66 J/mol=285.13 kJ/mol$

(1 J = 0.001 kJ )

285.13 is the maximum strength of a bond, in kJ/mol, that can be broken by absorption of a photon of 420-nm light.

c) the photodissociation reaction showing Lewis-dot structures is given in an image attached.