When the first electron gain enthalpy () of oxygen is kJ/mol, its second electron gain enthalpy is:

Question

When the first electron gain enthalpy () of oxygen is  kJ/mol, its second electron gain enthalpy is:

Canvas Classes · Accepted Answer

Strategy:
 Electron gain enthalpy () for the first electron of Oxygen is exothermic (negative). However, adding a second electron to an existing anion always requires energy to overcome electrostatic repulsion.

Step 1: Analyze the second electron gain
Equation: 
The incoming electron is repelled by the negative charge of the  ion. Energy must be supplied to force the electron into the orbital.
.

Result: The value is always positive.

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