Explain the concept of redox reactions and the ... - SS2 Chemistry Electrochemistry Question

Redox (reduction-oxidation) reactions involve the transfer of electrons between species. In a redox reaction, one species loses electrons (undergoes oxidation) while another species gains those electrons (undergoes reduction). Oxidation and reduction always occur together and are interconnected processes.

Oxidation numbers are assigned to atoms in a compound or ion to indicate the distribution of electrons within the molecule. They provide a way to track electron transfer in redox reactions. In general, oxidation numbers can be determined based on a set of rules:

●     The oxidation number of an element in its elemental form is zero (e.g., O2, Na, Cl2).

●     The oxidation number of a monatomic ion is equal to its charge (e.g., Na+ has an oxidation number of +1).

●     Oxygen typically has an oxidation number of -2, except in peroxides (e.g., H2O2) where it has an oxidation number of -1.

●     Hydrogen usually has an oxidation number of +1, except in metal hydrides (e.g., NaH) where it has an oxidation number of -1.

●     The sum of the oxidation numbers in a neutral compound is zero, and the sum in a polyatomic ion is equal to the ion's charge.

During a redox reaction, the oxidation numbers of certain elements change. The element that increases its oxidation number is oxidised, and the one that decreases its oxidation number is reduced. For example:

In the reaction: Zn + CuSO4 → ZnSO4 + Cu

●     Zinc (Zn) goes from an oxidation number of 0 to +2. It is oxidised (loses electrons) and is the reducing agent.

●     Copper (Cu) goes from an oxidation number of +2 to 0. It is reduced (gains electrons) and is the oxidising agent.