Many substances we use in the home are called bases. Dishwasher tablets, washing powder and cleaning liquids all contain bases. Antacid tablets used to treat indigestion contain the bases magnesium oxide or magnesium hydroxide. Bases can be oxides, hydroxides, or carbonates of metals. Ammonia is a base even though it does not contain a metal. If a base is soluble in water we call it an alkali. Alkalis dissolve in water to form hydroxide ions.
Chemical reactions of bases
Reactions with acids
Metal oxides and hydroxides react with acids to form a salt and water.
CaO (s) + 2HCl (aq) à CaCl2 + H2O
Calcium Oxide + Hydrochloric acid à Calcium Chloride + Water
NaOH (aq) + HNO3 (aq) à NaNO3 (aq) + H2O
Sodium hydroxide + nitric acid à Sodium nitrate + water
Metal carbonates react with acids to form a salt, water and carbon dioxide.
MgCO3 (s) + H2SO4 (aq) à MgSO4 (aq) + H2O (l) + CO2 (g)
Magnesium carbonate + sulfuric acid à Magnesium sulfate + water + carbon dioxide
When a base reacts with an acid to form a salt it's a neutralization reaction.
Reaction of alkalis with ammonium salts
Ammonium salts are much more violate than metal salts. When warmed with an alkali, ammonium salts decompose to form a metal salt, ammonia and water.
KOH (aq) + NH4Cl (aq) àHeatà KCl (aq) + NH3 (g) + H2O (l)
Potassium hydroxide + Ammonium chloride àHeatà Potassium chloride + Ammonia + water