Reactions of acids with metals
acidSubstance producing more hydrogen ions than hydroxide ions when dissolved in water. take part in reactions in which saltThe substance formed when the hydrogen ion in an acid is replaced by a metal ion. are produced. In these reactions, the hydrogen ionElectrically charged particle, formed when an atom or molecule gains or loses electrons. in the acids are replaced by metal ions.
Reactions of acids with metals
When acids react with metalShiny element that is a good conductor of electricity and heat, and which forms basic oxides., the products are a salt and hydrogen. In general:
Acid + metal → salt + hydrogen
For example:
Hydrochloric acid + magnesium → magnesium chloride + hydrogen
2HCl(aq) + Mg(s) → MgCl2(aq) + H2(g)
Zinc and iron also react with hydrochloric acid.
Magnesium, zinc and iron also react with sulfuric acid. The products are a salt (in this case a sulfate) and hydrogen. For example:
sulfuric acid + iron → iron(II) sulfate + hydrogen
H2SO4(aq) + Fe(s) → FeSO4(aq) + H2(g)
Question
Name the two products of the reaction of zinc with hydrochloric acid.
The products are zinc chloride and hydrogen.
Question
Name the products of the reaction between zinc and sulfuric acid, and write an equation for the reaction.
The products are zinc sulfate and hydrogen.
H2SO4(aq) + Zn(s) → ZnSO4(aq) + H2(g)
Explaining the reactions of acids with metals - Higher
The reactions of acids with metals are redox reactionWhen reduction and oxidation take place at the same time.. For example, the ionic equationA chemical equation that shows how positively charged ions join with negatively charged ions to make a compound. for the reaction of magnesium with hydrochloric acid is:
2H+(aq) + Mg(s) → Mg2+(aq) + H2(g)
This ionic equation can be split into two half equationAn equation, involving ions and electrons, that describes the process happening at an electrode.:
- Mg(s) → Mg2+(aq) + 2e-(oxidation)
- 2H+(aq) + 2e- → H2(g) (reduction)
Notice that:
- magnesium atoms lose electronSubatomic particle, with a negative charge and a negligible mass relative to protons and neutrons. - they are oxidationThe gain of oxygen, or loss of electrons, by a substance during a chemical reaction.
- hydrogen ions gain electrons - they are reductionThe loss of oxygen, gain of electrons, or gain of hydrogen by a substance during a chemical reaction.
Reduction and oxidation happen at the same time, so the reactions are called redox reactions.
Question
Use half equations to explain why the reaction of zinc with sulfuric acid is a redox reaction.
The two half equations are:
- Zn(s) → Zn2+(aq) + 2e-
- 2H+(aq) + 2e- → H2(g)
Zinc atoms lose electrons, so they are oxidised. Hydrogen ions gain electrons, so they are reduced. Since reduction and oxidation happen at the same time, the reaction is a redox reaction.