Question

Photoelectrons are removed with kinetic energy 1.864×10^-21 J, when photons of light with energy 4.23×10^-19 J fall on the metal. What is the minimum energy required per mole to remove an electron from potassium metal?

Answer 1

The minimum energy required to remove an electron from a potassium metal can be obtained by subtracting the energy of the incident photons from the kinetic energy of the removed photoelectrons. Based from the given values, the following equation is obtained:

Minimum energy required = 4.23×10^-19 J - 1.864×10^-21 J

We then get 4.2114 x 10^-19 J as the minimum energy required to remove the electron. We then convert this into units of energy per mole. This is to be done by using Avogadro's number which result to the following equation:

Minimum energy required per mole = 4.2114 x 10^-19 J x 6.022 x 10^23 mol^-1

The final answer is then 253.608 kJ/mol