Reactions of Acids (Edexcel IGCSE Chemistry (Modular))

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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 saltcarbon 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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