When the first electron gain enthalpy ΔegH of oxygen is-141 kJ/mol, its second electron gain enthalpy is

As given, the first electron gain enthalpy of oxygen can be shown as, O(g)+e−⟶O−(g),ΔegH1=−141kJ/mol The expression of second electron gain enthalpy of oxygen will be,O−(g)+e−⟶O2−(g),ΔegH2=+ ve ΔegH2 of oxygen is positive, i.e. endothermic, because a strong electrostatic repulsion will be observed between highly negative O and the incoming electron (e-).A very high amount of energy will be consumed (endothermic) by the system to overcome the electrostatic repulsion.