Question

a photochemical reaction requires 9.6 into 10 power 16 energy per molecule calculate the number of photons per molecule of light with wavelength 250 nm that is just sufficient to initiate the reaction ​

Answer 1

Answer :The number of photons per molecule is, 1206

Solution :

First we have to calculate the energy of photons.

Formula used :

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

where,

E = energy of photon = ?

h = Planck's constant = $6.63\times 10^{-34}Js$

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

$\lambda$ = wavelength = $250nm=250\times 10^{-9}m$

Now put all the given values in the above formula, we get the energy of the photons.

$E=\frac{(6.63\times 10^{-34}Js)\times (3\times 10^8m/s)}{250\times 10^{-9}m}$

$E=7.96\times 10^{-19}J$

The energy of photons  is, $7.96\times 10^{-19}J$

Now we have to calculate the number of photons per molecule.

$\text{Number of photons}=\frac{\text{Total energy}}{\text{Energy of photon}}$

$\text{Number of photons}=\frac{9.6\times 10^{-16}J}{7.96\times 10^{-19}J}=1206$

Therefore, the number of photons per molecule is, 1206