Question

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

• A. 253.6 J/mol
• B. 326 KJ/mol
• C. 253.6 KJ/mol
• D. 453 KJ/mol

Answer 1

Answer: (C)

253.6 KJ/mol

Minimum energy required = $4.23\times {10}^{-19}J-1.86\times {10}^{-21}J$

= $4.2114\times {10}^{-19}J$

This is the minimum energy required to remove the electron.

We then convert into units of energy per mole.

Minimum energy required per mole $=4.2114\times {10}^{-19}J\times 6.022\times {10}^{23}mo{l}^{-1}$

$=253.608$ KJ/mol