Question

Identify the energy change that occurs when an electron is added to an O− ion, forming an oxide (O2−) ion:

O−(g)+e−→O2−(g)
ANSWER:

a. −142 kJ
b. +710 kJ
c. +142 kJ
d. −710 kJ

Answer 1

The energy change that occurs when an electron is added to an O- ion, forming an oxide (O2-) ion is +142 kJ.

Step-by-step explanation:

The energy change that occurs when an electron is added to an O- ion, forming an oxide (O2-) ion is +142 kJ. This means that energy is required for this process to occur. The electron affinity (EA) for the first electron added to the O- ion is -141 kJ/mol, which is exothermic. However, the electron affinity for the second electron added to form the O2- ion is +744 kJ/mol, which is endothermic. The overall energy change is the sum of these two values, resulting in +142 kJ.