Which equation represents the oxidation half-reaction for this redox reaction?

Mg + CuSO4 d MgSOÁ + Cu

-Mg - >Mg

-Mg - > Mg+O4

-Mg - > Mg+2e-

-Mg - > Mg+3e-

The oxidation half-reaction for the redox reaction is that which involves the substance whose oxidation number increased. From the choices above, the answer is the third choice. Magnesium on the left side of the equation has an oxidation number of 0 because it is uncharged pure substance. One the right side, it's oxidation state is + 2 where 2 electrons should be added to it to equate the number of electrons on both sides.