Redox Reactions: Understanding Reducing Agents

What are Redox Reactions?

Redox reactions, short for reduction-oxidation reactions, involve a transfer of electrons between two species. One species loses electrons (oxidation), and another species gains electrons (reduction). These processes always occur together.

Oxidation and Reduction Defined

• Oxidation: The loss of electrons by a substance. This involves an increase in oxidation state.
• Reduction: The gain of electrons by a substance. This involves a decrease in oxidation state.

Reducing Agents: The Definition

A reducing agent is a substance that causes another substance to be reduced. Crucially, in the process of reducing another substance, the reducing agent itself is oxidised. It donates electrons to the other substance.

How Reducing Agents Work

Reducing agents have a high tendency to lose electrons. They readily donate electrons to other substances, thereby facilitating the reduction of those substances. Because they lose electrons, their own oxidation state increases.

Example Reaction

Consider the reaction between sodium (Na) and chlorine (Cl₂):

$2Na + Cl_2 \rightarrow 2NaCl$

In this reaction:

• Sodium (Na) is the reducing agent. It loses an electron to become a sodium ion ($Na^+$), undergoing oxidation.
• Chlorine (Cl₂) is the oxidizing agent. It gains electrons to become a chloride ion ($Cl^-$), undergoing reduction.

Table Summarizing Reducing Agents

Property	Description
Definition	A substance that causes reduction and is itself oxidised.
Electron Donating Tendency	High
Oxidation State Change	Increases during the reaction.
Example	Sodium (Na), Magnesium (Mg), Zinc (Zn)

Common Reducing Agents

Some common examples of reducing agents include:

• Metals (e.g., Sodium, Magnesium, Zinc, Iron)
• Hydrogen (H₂)
• Hydrides (e.g., NaH, LiAlH₄)