Reactivity Series of Metals

Metals and Reactivity

• A few reactive metals react with cold water, producing a metal hydroxide and hydrogen gas (e.g., 2K + 2H2O -> 2KOH + H2 with potassium).
• Most metals react with acid, producing a salt and hydrogen gas (acid + metal -> salt + H2).

Reactivity Series

• Metals can be arranged in a reactivity series based on their reactions with water, dilute hydrochloric or sulfuric acid, and oxygen.
• The order of reactivity is: potassium, sodium, lithium, calcium, magnesium, aluminium, zinc, iron, copper, silver, gold.
• Metals can be arranged in a reactivity series based on their displacement reactions between metals and metal oxides, and metals and aqueous solutions of metal salts.

Displacement Reactions

• A more reactive metal can displace a less reactive metal from a compound in a displacement reaction.
• Displacement reactions can be used to determine the relative reactivity of metals.

Rusting of Iron

• Iron rusts when both air and water are present, resulting in corrosion (oxidation).
• Rusting can be prevented by excluding oxygen and water, such as by painting, coating with plastic, or using oil or grease.

Prevention of Rusting

• Barrier methods: painting, coating with plastic, using oil or grease.
• Galvanising: using a more reactive metal (e.g., zinc) to protect iron from rusting.
• Sacrificial protection: using a more reactive metal to protect iron from rusting.

Oxidation and Reduction

• Oxidation: gain of oxygen OR loss of electrons.
• Reduction: loss of oxygen OR gain of electrons.
• Redox: a reaction in which both oxidation and reduction occur.
• Oxidising agent: causes another reactant to be oxidised and is reduced itself.
• Reducing agent: causes another reactant to be reduced and is oxidised itself.

Investigating Reactions

• Investigate reactions between dilute hydrochloric and sulfuric acids and metals (e.g., magnesium, zinc, and iron).
• The reactivity series diagram shows that only more reactive metals react with dilute acids (up to iron).