Final answer:
The redox reaction can be balanced by separating it into oxidation and reduction half-reactions, where HNO3 is the oxidizing agent and sulfur (S) is the reducing agent. The MnO4 and SO2 act as oxidizing and reducing agents, respectively, in another example. Charge balance in redox reactions ensures conservation of charge.
Step-by-step explanation:
To balance the redox reaction given by S(s) + HNO3(aq) -> H2SO3(aq) + N2O(g) in acidic conditions, we need to write and balance the half-reactions for oxidation and reduction separately.
- Oxidation half-reaction: S(s) -> H2SO3(aq)
- Reduction half-reaction: HNO3(aq) -> N2O(g)
During the balancing process, we would balance each half-reaction for elements and charge, and then combine them, ensuring mass and charge conservation. After balancing, it becomes apparent that the oxidizing agent is HNO3 and the reducing agent is sulfur (S).
To answer Exercise 8.2.2: In the reaction MnO4 + SO2 → Mn²+ + SO4²-, the oxidizing agent is MnO4 (permanganate ion) as it gains electrons (is reduced), and the reducing agent is SO2 (sulfur dioxide) as it loses electrons (is oxidized).
Charge balance is essential in redox reactions because the law of conservation of charge dictates that the total charge must remain constant throughout the reaction. As a result, the number of electrons lost in oxidation must be equal to the number gained in reduction.