Question

A light emitting diode (L.E.D.) emits photons with an energy of `2.84 xx 10^-19` J. What is the energy per mole of photons emitted?

Answer 1

The molar energy of the photons is 171 kJ/mol.

Explanation:

Just as a dozen is twelve of anything, so a mole is Avogadro's number = `6.02×10^{23}` of anything. So the energy of the given light beams may be rendered as

`(2.84×10^{-19}"J")×({6.02×10^{23}}/{"mole"})=1.71×10^5{"J"}/{"mole"}`.

This is similar in magnitude to the energy involved in chemical reactions, accounting for the fact that light often drives chemical reactions. One real-world example of this is given in https://en.wikipedia.org/wiki/Photosynthesis.