9.1.3 Oxidizing & Reducing agents

Oxidising agent

• An oxidising agent is a substance that oxidises another atom or ion by causing it to lose electrons
• An oxidising agent itself gets reduced – gains electrons
• Therefore, the ox. no. of the oxidising agent decreases

Example of an oxidising agent in a chemical reaction

Reducing agent

• A reducing agent is a substance that reduces another atom or ion by causing it to gain electrons
• A reducing agent itself gets oxidised – loses/donates electrons
• Therefore, the ox. no. of the reducing agent increases

Example of a reducing agent in a chemical reaction

• For a reaction to be recognised as a redox reaction, there must be both an oxidising and reducing agent
• Some substances can act both as oxidising and reducing agents
• Their nature is dependent upon what they are reacting with and the reaction conditions

Oxidising & Reducing Agents Table

• Applying the definitions of oxidising and reducing agents allows you to identify them in chemical equations
• By deducing the oxidation numbers of the species you can determine whether it has been oxidised or reduced

A visual reminder of oxidation numbers and redox. This is like an elevator in a building going up to higher floors is oxidation and going down to the basement is reduction

Answer:

The correct option is B.

• • Oxidising agents are substances that oxidise other species, gain electrons and are themselves reduced.
  • Write down the oxidation numbers of each species in the reaction

• • In equation B, Fe²⁺ oxidises Mg(0) to Mg²⁺(+2) and is itself reduced from Fe²⁺(+2) to Fe(0)