When a sample of Mg(s) reacts completely with O2(g), the Mg(s) loses 5.0 moles of electrons. How many moles of electrons are gained by the O2(g)? *

if magnesium looses five moles of electrons, oxygen will also gain five moles of electrons.!

Explanation:

Oxidation refers to the loss of electrons. Any specie that looses electrons in a redox reaction is said to be the reducing agent. Hence the reducing agent participates in the oxidation half equation. In this case, magnesium is the reducing agent.

Reduction has to do with the gain of electrons. The oxidizing agent participates in the reduction half equation. Hence the oxidizing agent is reduced in the redid reaction. The reducing agent in this case is the oxygen molecule.

Oxidation half equation;

Mg(s)> Mg^2+(aq) + 2e

Reduction half equation;

O2(g) + 2e > 2O^2-(aq)

From the balanced reaction equation, two moles of electrons is transferred.

Hence if magnesium looses five moles of electrons, oxygen will also gain five moles of electrons.