Which of the following half-reactions represents the reduction of Fe2+ to Fe(s)?

The reduction half-reaction of Fe2+ to Fe(s) involves the gain of electrons by the iron ion. In electrochemistry, a reduction process is defined as the gain of electrons, leading to a decrease in the oxidation state of the species.

In the half-reaction presented, Fe2+ receives two electrons (2e-) to transform into solid iron (Fe). The formula highlights that for every Fe2+ ion, two electrons are needed to complete the reduction process. This change illustrates how Fe2+, which is in the +2 oxidation state, is converted to Fe, which is in the zero oxidation state, indicating reduction.

This accurately describes the fundamental principles of a reduction reaction. The other choices represent different processes that either depict oxidation, combine iron with hydroxide ions, or involve other oxidation states, and do not indicate the reduction of Fe2+.