Given the reaction:
2Li(s) + Cl2(g) -> 2LiCl(s)
As the reaction takes place, the Cl2(g) will:
A. lose protons.
B. gain protons.
C. gain electrons.
D. lose electrons.
E. remain constant.
Eliminate choices 3 and 4 because only electrons are lost or gained in oxidation-reduction reactions. Write the half reaction for Cl2(g):
Cl2(g) + 2e- -> 2Cl-(s)
(In 2LiCl(s), Li has an oxidation number of +1. 2 times +1 = +2; therefore Cl must have an oxidation number of -2). Cl on the left side of the equation had an oxidation number of 0. It has to gain 2 electrons to have an oxidation of -2.