Reactions of Acids (Edexcel IGCSE Chemistry: Double Science)

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 → MSO4 + 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