(HANDOUT) IGCSE Chemistry-Redox Reactions

REDOX REACTIONS

• Redox stands for reduction oxidation.
• Redox reaction, also called oxidation reduction reaction, is a chemical reaction in which one substance is reduced and another is oxidised simultaneously.
• Oxidation and reduction of substances occur simultaneously. As one substance is reduced the other is oxidised.
• An oxidising agent is a substance that causes the oxidation of the other substance. Therefore, the substance that is reduced in a reaction is the oxidising agent.
• A reducing agent is a substance that causes the reduction of the other substance. For example, the substance that is oxidised in a reaction is the reducing agent.

OXYGEN IN REDOX REACTION

• Oxidation is the gain of oxygen by the substance. A substance that has gained oxygen is said to be oxidised.
• Reduction is the loss of oxygen by the substance. A substance that has lost oxygen is said to be reduced.

HYDROGEN IN REDOX REACTION

• Oxidation is the loss of hydrogen by the substance. A substance that has lost hydrogen is said to be oxidised.
• Reduction is the gain of hydrogen by the substance. A substance that has gained hydrogen is said to be reduced.

ELECTRONS IN REDOX

• Oxidation is the loss of electrons. A substance that loses electrons is oxidised.
• Reduction is the gain of electrons. A substance that gains electrons is reduced.
• The reaction below shows a redox reaction involving the gain and loss of electrons. 

OXIDATION NUMBER

• Oxidation number, also called oxidation state, is the number of electrons an atom gains or losses in a chemical combination.