Acids, bases, and neutralisation

• All acids contain hydrogen in their formulae. When dissolved in water, an acid releases hydrogen ions as protons into solution.
• $HCl(g) +$$aq -> H^+$$(aq) +$$Cl^-$

  Hydrogen chloride gas releases H+ ions as it dissolves in water. In this equation +aq has been included to show tht an excess of water is present. The equation is essentially hydrogen chloride gas dissolving to for an aqueous solution
• A strong acid releases all its hydrogen atoms as ions in solution and completely dissociates in aqueous solution.
• A weak acid only releases a small proportion of its available hydrogen atoms into solution as H+ ions. It partially dissociates in aqueousolution
• Not all compounds that contain hydrogen atoms are acids. Each molecule of ethanoic acid contains 4 hydrogen atoms, but only the hydrogen atom on the COOH group is released as H+. Even then, only about one molecule in every hundred dissociates, so ethanoic acid is a weak acid. Most organic acids are weak acids
• Metal oxides, metal hydroxides, metal carbonates, and ammonia are classified as bases.
• A base neutralises an acid to form a salt
• An alkali is a base that dissolves in water releasing hydroxide ions OH- into the solution.
• In neutralisation of an acid, H+ (aq) ions react with a base to form a salt and neutral water. The H+ ions from the acid are replaced by the metal or ammonium ions from the base
• An acid is neutralised by a metal oxide or metal hydroxide to form a salt and water only
• An acid is neutralised by an alkali to form a salt and water only. With alkalis, the reactants are in solution.
• The ionic equation of a neutralisation with an alkali is much simpler than the overall equation: neutralisation of H+ (aq) ions by OH- (aq) ions to form neutral water H2O(l)
• Carbonates neutralise acids to form a salt, water, AND carbon dioxide