Reactions of Acids (Edexcel IGCSE Chemistry (Modular))
Revision Note
Reactions of Acids
Reactions of acids with metals
Only metals above hydrogen in the reactivity series will react with dilute acids
The more reactive the metal then the more vigorous the reaction will be
Metals that are placed high on the reactivity series such as potassium and sodium are very dangerous and react explosively with acids
When acids react with metals they form a salt and hydrogen gas
The general equation is:
metal + acid ⟶ salt + hydrogen
Some examples of metal-acid reactions and their equations are given below:
Table of acid-metal reactions
Metal | Sulfuric acid | Hydrochloric acid |
|---|---|---|
Magnesium | Mg (s) + H2SO4 (aq) → MgSO4 (aq) + H2 (g) | Mg (s) + 2HCl (aq) → MgCl2 (aq) + H2 (g) |
Zinc | Zn (s) + H2SO4 (aq) → ZnSO4 (aq) + H2 (g) | Zn (s) + 2HCl (aq) → ZnCl2 (aq) + H2 (g) |
Iron | Fe (s) + H2SO4 (aq) → FeSO4 (aq) + H2 (g) | Fe (s) + 2HCl (aq) → FeCl2 (aq) + H2 (g) |
In general, we can summarise the reaction of a metal that forms a +2 ion as follows:
Acids-Metals Summary Table
Acid | Name of products | Equation for reaction |
|---|---|---|
Hydrochloric acid | Metal chloride and hydrogen | M + 2HCl → MCl2 + H2 |
Sulfuric acid | Metal sulfate and hydrogen | M + H2SO4 → MCl2 + H2 |
Reaction of acids with bases
When an acid reacts with a base, a neutralisation reaction occurs
In all acid-base neutralisation reactions, a salt and water are produced:
acid + base ⟶ salt + water
The identity of the salt produced depends on the acid used and the positive ions in the base
Hydrochloric acid produces chlorides, sulfuric acid produces sulfate salts and nitric acid produces nitrates
Metal oxides and metal hydroxides act as bases
The following are some specific examples of reactions between acids and metal oxides / hydroxides:
2HCl + CuO ⟶ CuCl2 + H2O
H2SO4 + 2NaOH ⟶ Na2SO4 + 2H2O
HNO3 + KOH ⟶ KNO3 + H2O
In general, we can summarise the reaction of metals and bases as follows:
Acids and Metals Oxides or Hydroxides Summary Table
Acid | Name of products | Equation for reaction |
|---|---|---|
Hydrochloric acid | Metal chloride and water | MOH + HCl ⟶ MCl + H2O |
Sulfuric acid | Metal sulfate and water | MO + H2SO4 ⟶ MSO4 + H2O |
Nitric acid | Metal nitrate and water | MO + HNO3 ⟶ MNO3 + H2O |
Reactions of Acids with Metal Carbonates
Acids will react with metal carbonates to form the corresponding metal salt, carbon dioxide and water
These reactions are easily distinguishable from acid – metal oxide/hydroxide reactions due to the presence of effervescence caused by the carbon dioxide gas
Acids & Metal Carbonates Reactions Table
Acid | Name of Products | Equation for Reaction |
|---|---|---|
Hydrochloric acid | Metal chloride, carbon dioxide and water | MCO3 + 2HCl ⟶ MCl2 + CO2 + H2O |
Sulfuric acid | Metal sulfate, carbon dioxide and water | MCO3 + 2H2SO4 ⟶ MSO4 + CO2 + H2O |
Nitric acid | Metal nitrate, carbon dioxide and water | MCO3 + HNO3 ⟶ M(NO3)2 + CO2 + H2O |
The following are some specific examples of reactions between acids and metal carbonates:
2HCl + Na2CO3 ⟶ 2NaCl + H2O + CO2
H2SO4 + CaCO3⟶ CaSO4 + H2O + CO2
Examiner Tip
If in an acid-base reaction there is effervescence produced then the base must be a metal carbonate which produces carbon dioxide gas.
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