Question

what happens with the referenced oxidation number when the element with which it is associated has been reduced?

○ decrease

○ increase

Explanation:

In redox chemistry, reduction is defined as the gain of electrons. When an element is reduced, its oxidation number decreases because gaining electrons (which are negatively charged) lowers the overall positive charge (or increases the negative charge) of the species, thus reducing the oxidation number. For example, in the reaction $\ce{Cu^{2+} + 2e^- -> Cu}$, the oxidation number of Cu goes from +2 to 0, which is a decrease.

Answer:

A. decrease