Question

Would you expect the second electron gain enthalpy of O as positive, more negative or less negative than the first? Justify your answer.

Answer 1

O(g) + e ---------> O- (g) ; H= -141 KJ/mol

O-(g) + e ---------> O^2-(g) ; H= +780 KJ/mol.

see above equations and electron gain enthalpy of O and O- . you observed that ,

electron gain enthalpy of O is negative while electron gain enthalpy of O- is positive .

when an electron is added to Oxygen atom to form O- ion , energy is released . hence, first electron gain enthalpy of oxygen is negative .

But when another electron is add to O- ion to form O2- ion , it feels stronger electrostatic repulsion. hence, when we add 2nd electron , then energy absorb by it. that's why the 2nd electron gain enthalpy of oxygen is positive.

Answer 2

Explanation:

hope it will help you...