1 Acids, bases, alkalis and neutralisation

An Alkali is a soluble base that releases OHions in aqueous solution; The most common alkalis are sodium hydroxide (NaOH), potassium hydroxide (KOH) and aqueous ammonia (NH3 ) 2.1.4 Acids An acid releases H+ ions in aqueous solution There are several definitions of acids we use in chemistry. One we use later in the course is the Bronsted- Lowry acid which is a defined as a proton (H+ ) donor The most common strong acids are : Hydrochloric ( HCl), sulphuric (H2SO4 ) and nitric (HNO3 ) acid; Ethanoic acid CH3COOH is a weak acid A Salt is formed when the H+ ion of an acid is replaced by a metal ion or an ammonium ion Observations : In carbonate reactions there will be Effervescence due to the CO2 gas evolved and the solid carbonate will dissolve Bases and Alkalis Bases neutralise acids. Common bases are metal oxides, metal hydroxides and ammonia. The Bronsted- Lowry base is defined as a proton (H+ ) acceptor A base readily accepts H+ ions from an acid: eg OHions accepts an H+ ion forming H2O NH3 accepts an H+ ion forming NH4+ ion Neutralisation Reactions Neutralisation reaction form salts ACID + BASE  SALT + WATER 2HNO3 + Mg(OH)2  Mg(NO3 )2 + 2H2O 2HCl + CaO  CaCl2 +H2O Acid + Carbonate  Salt + Water + Carbon Dioxide H2SO4 + K2CO3  K2SO4 + CO2 + H2O HCl + NH3  NH4Cl Strong acids completely dissociate when dissolved in water Weak acids only slightly dissociate when dissolved in water, giving an equilibrium mixture