Question

For the gaseous reaction, $K+F\to K^{+}+F^{-},\Delta H$ was calculated to be $19kcal$ under conditions where the cations and anions were prevented by electrostatic separation from combing with each other. The ionization potential of $K$ is $4.3eV$. What is the electorn affinity of $F$?

Answer 1

For $1$ $mole$, $\Delta H=19$ $Kcal=19\times 2.611\times {10}^{22}=4.96\times {10}^{23}$ $eV/mol$

For $1$ $atom$, $\Delta H=\frac{4.96\times {10}^{23}}{6.023\times {10}^{23}}=0.8$ $eV/atom$

Electron affinity of $F$ is $4.3-0.8=3.476$ $eV$