Question

The electron gain enthalpy of oxygen atom is $1.41\times {10}^{5}Jmo{l}^{-1}$. Energy required $\left(inkJ\right)$ to oxidise 4 g of $O^{-}$ ions into oxygen atom is

Answer 1

Electron gain enthalpy of oxygen atom:
$O+e^{-}\to O^{-}$
$\Delta H=-1.41\times {10}^{5}Jmo{l}^{-1}$
$=-141kJmo{l}^{-1}$
Ionisation Enthalpy of $O^{-}$ ion:
$O^{-}\to O+e^{-}$
$\Delta H=141kJmo{l}^{-1}$
Energy required when 4 g of $O^{-}$ is taken
$=\frac{4}{16}\times 141=35.25kJ$