Question:
When the first electron gain enthalpy $\left(\Delta_{\text {eg }} \mathrm{H}\right)$ of oxygen is $-141 \mathrm{~kJ} / \mathrm{mol}$, its second electron gain enthalpy is :
Correct Option: , 3
Solution:
Second electron gain enthalpy is always positive for every element.
$\mathrm{O}_{(\mathrm{g})}^{-}+\mathrm{e}^{-} \rightarrow \mathrm{O}_{(\mathrm{g})}^{-2} \quad ; \Delta \mathrm{H}=$ positive