Types of chemical reactions - Cambridge OCR GatewayOxidation and reduction
Oxidation is the gain of oxygen and reduction is the loss of oxygen. Neutralisation is the reaction between an acid and a base. Acids react with metals, bases and carbonates to produce salts.
magnesium is oxidiseChemical substances are oxidised by the addition of oxygen, removal of hydrogen or the removal of electrons. to form magnesium oxide
copper(II) oxide is reduceA substance is reduced if it loses oxygen or gains electrons. to form copper
This is an example of a redox reactionOxidation and reduction always take place together. The combined reaction is called a redox reaction. because reduction and oxygen happen at the same time. Also in this reaction:
magnesium acts as a reducing agentA substance that loses electrons very easily (for example, group 1 elements). because it can reduce copper(II) oxide
copper(II) oxide acts as an oxidising agentA substance that can oxidise other substances in chemical reactions. because it can oxidise magnesium
Question
Aluminium reacts with zinc oxide:
aluminium + zinc oxide → aluminium oxide + zinc
Explain which substance is oxidised and which substance acts as an oxidising agent.
Aluminium is oxidised because it gains oxygen to form aluminium oxide. Zinc oxide acts as an
oxidising agent because it can oxidise aluminium.
Question
Carbon monoxide reacts with iron(III) oxide:
carbon monoxide + iron(III) oxide → carbon dioxide + iron
Explain which substance is reduced and which substance acts as a reducing agent.
Iron(III) oxide is reduced because it loses oxygen to form iron. Carbon monoxide acts as a reducing
agent because it can reduce iron(III) oxide.
Loss or gain of electrons - Higher
In terms of electrons in a chemical reaction:
oxidation is the loss of electrons
reduction is the gain of electrons
These definitions are useful in reactions that do not involve oxygen. For example, magnesium reacts with chlorine to form magnesium chloride:
Mg + Cl2 → MgCl2
Magnesium chloride contains Mg2+ ions and Cl- ions. The balanced equation can be split into two half equations:
