Question

Green light has a wavelength of 505nm. What is the energy, in joules, of one photon of green light? What is the energy, in joules , of 5.00 mol of photons of green light?

Answer 1

1)

Given:

lambda = 5.05*10^-7 m

use:

E = h*c/lambda

=(6.626*10^-34 J.s)*(3.0*10^8 m/s)/(5.05*10^-7 m)

= 3.936*10^-19 J

This is energy of 1 photon

Answer: 3.94*10^-19 J

2)

Now find the energy of 1 mol of photon.

Energy of 1 mol = energy of 1 photon * Avogadro's number

= 3.936*10^-19*6.022*10^23 J/mol

= 2.37*10^5 J/mol

= 2.37*10^2 KJ/mol

So,

Energy of 5.00 mol = number of mol * Energy of 1 mol

= 5.00 mol * 2.37*10^2 KJ/mol

= 1.18*10^3 KJ

= 1.18*10^6 J

Answer: 1.18*10^6 J