Final answer:
The complementary half-reaction balancing the oxidation of zinc (Zn to Zn²+ + 2eˆ) would be a reduction reaction, such as Fe³+ gaining electrons to become Fe²+. When combined, these half-reactions maintain electrical neutrality, as required in redox reactions.
Step-by-step explanation:
The complementary half-reaction needed to balance the given oxidation half-reaction, Zn(s) → Zn²+(aq) + 2eˆ, is a reduction half-reaction where something else gains the two electrons that zinc loses. The general form of a reduction reaction is A + neˆ → B, where A is the oxidized form that will gain electrons and B is the reduced form. In this particular case, any species that can accept two electrons could balance the zinc oxidation reaction. For instance, two hydrogen ions (2H+) can gain two electrons to form hydrogen gas, leading to the reduction half-reaction 2H+(aq) + 2eˆ → H₂(g).
If we look at the provided examples, the reduction of Fe³+ to Fe²+ is a suitable complementary reaction because it involves the gain of one electron. Therefore, the balanced equation would be:
- Oxidation: Zn(s) → Zn²+(aq) + 2eˆ
- Reduction: 2eˆ + 2 Fe³+(aq) → 2 Fe²+(aq)
Adding the two half-reactions gives the overall chemical reaction, which is electrically neutral with a net charge of zero on both sides. This aspect of a redox reaction being balanced, when the number of electrons lost equals the number of electrons gained, is essential for the conservation of charge.