For each of the following balanced oxidation–reduction reactions, (i) identify the oxidation numbers for all the elements in the reactants and products and (ii) state the total number of electrons transferred in each reaction. (a) 2 MnO₄^-(aq) + 3 S^2-(aq + 4 H₂O(l) → 3 S(s) + 2 MnO₂(s) + 8 OH^-(aq)

Key Concepts

Oxidation Numbers

Oxidation numbers are assigned to atoms in a compound to indicate their degree of oxidation or reduction. They help in identifying which atoms are oxidized and which are reduced during a redox reaction. The rules for assigning oxidation numbers include that the oxidation number of an element in its elemental form is zero, and for monoatomic ions, it equals the charge of the ion.

Redox Reactions

Redox (reduction-oxidation) reactions involve the transfer of electrons between two species. In these reactions, one species is oxidized (loses electrons) while another is reduced (gains electrons). Understanding the electron transfer is crucial for determining the total number of electrons transferred, which is essential for balancing the reaction and understanding its stoichiometry.

Balancing Redox Reactions

Balancing redox reactions requires ensuring that both mass and charge are conserved. This often involves separating the reaction into half-reactions for oxidation and reduction, balancing each half for mass and charge, and then combining them. The total number of electrons transferred can be determined from the balanced half-reactions, providing insight into the stoichiometry of the overall reaction.