Solveeit Logo
Login

Question

Question: When the first electron gain enthalpy ($\Delta_{eg}$H) of oxygen is -141 kJ/mol, its second electron...

When the first electron gain enthalpy (Δeg\Delta_{eg}H) of oxygen is -141 kJ/mol, its second electron gain enthalpy is

A

A more negative value than the first

B

Almost the same as that of the first

C

Negative, but less negative than the first

D

A positive value

Answer

A positive value

Explanation

Solution

The first electron gain enthalpy is for the process: O(g) + e−^- →\rightarrow O−^- (g). This is exothermic as oxygen is electronegative. The second electron gain enthalpy is for the process: O−^- (g) + e−^- →\rightarrow O2−^{2-} (g). In this case, an electron is being added to an already negatively charged ion (O−^-). This addition is unfavorable due to electrostatic repulsion between the incoming electron and the negative charge on the ion. Therefore, energy must be supplied to overcome this repulsion, making the second electron gain enthalpy positive (endothermic).