4.1 Acids, Bases and Neutralisation

4.1 Acids, Bases and Neutralisation

1. Acids

   • All contain hydrogen in their formulae
   • When dissolved in water, release hydrogen ions as protons H+ into the solution
   • Hydrogen chloride gas releases H+ ions as is dossolves in water
     • HCl (g) + aq --> H+ (aq) + Cl- (aq)

2. Strong and Weak Acids

   • Strong Acid
     • Releases all its hydrogen atoms into solution as H+ ions
     • Fully Dissociates
     • E.g/ Hydrochloric Acid (HCl)
   • Weak Acid
     • E.g/ Ethanoic Acid (CH3COOH)
     • Releases only a small proportion of its available hydrogen atoms into solution as H+ ions
     • Partially Dissociates

3. Bases and Alkalis

   • Bases
     • Metal Oxides
     • Metal Hydroxides
     • Metal Carbonates
     • Ammonia (NH3)
     • A base neutralises an acid to form a salt
   • Alkalis
     • An alkali is a base that dissolves in water releasing hydroxide ions (OH-) into the solution
     • Sodium Hydroxide releasing hydroxide ions as it dissolves in water
       • NaOH (s) + aq --> Na+ (aq) + OH- (aq)

4. Neutralisation

   • In neutralisation of an acid, H+ ions react with a base to form a salt and neutral water
     • H+ ions from the acid are replaced by metal or ammonium ions from the base
   • Neutralisation of Acids with Metal Oxides and Hydroxides
     • Acid + Metal Oxide --> Salt + Water
     • Acid + Metal Hydroxide --> Salt + Water
     • Neutralisation of sulphuric acid and hydrochloric acid by Copper(II) oxide to form a salt and water only
       • CuO (s) + H2SO4 (aq) --> CuSO4 (aq) + H2O (l)
       • CuO (s) + 2HCl (aq) --> CuCl2 (aq) + H2O (l)
   • Alkalis
     • Reactants in solution
     • Acid + Alkali --> Salt + Water
     • Ionic Equation
       • H+ (aq) + OH- (aq) --> H2O (l)
   • Neutralisation of acids with Carbonates
     • Acid + Metal Carbonate --> Salt + Water + Carbon Dioxide
     • Neutralisation of two carbonates by sulphuric acid and hydrochloric acid
       • ZnCO3 (s) + H2SO4 --> ZnSO4 + H2O + CO2
       • MgCO3 + 2HCl (aq) --> MgCl2 (aq) + H2O (l) + CO2 (g)