When balancing reactions in Chapter 3, we did not mention that reactions must be charge balanced as well as mass balanced. What do charge balance and mass balance mean? How are redox reactions charge balanced?

Charge balance means that the total charge on the reactant side of a chemical reaction must be equal to the total charge on the product side. In other words, the net charge must be conserved during the reaction. Mass balance, on the other hand, means that the number of each type of atom on the reactant side must be equal to the number of each type of atom on the product side. Conservation of mass ensures that atoms are not created or destroyed during the reaction.

Redox reactions are chemical reactions where there is a transfer of electrons between two species. During this process, one species is reduced (gains electrons) while the other species is oxidized (loses electrons). The species that gains electrons is called the oxidizing agent, and the species that loses electrons is called the reducing agent.

To balance charge in a redox reaction, the number of electrons gained and lost must be equal. This is done by finding the least common multiple of the two half-reactions (reduction and oxidation half-reaction) and multiplying each half-reaction with the appropriate integer to match the number of electrons gained and lost in each half-reaction. Finally, the half-reactions are combined to give a balanced redox reaction. In summary, balancing a redox reaction involves: 1. Identifying the oxidation and reduction half-reactions. 2. Balancing each half-reaction for mass (number of atoms). 3. Balancing each half-reaction for charge by adding electrons to either the reactant or product side. 4. Matching the number of electrons in each half-reaction by finding the least common multiple. 5. Combining the half-reactions and simplifying to obtain the balanced redox reaction. By following these steps, we ensure that redox reactions are both charge balanced (equal number of electrons gained and lost) and mass balanced (equal number of atoms for each element on both sides of the reaction).