acids and bases

-a substance which has the ability to donate H+ ions -when dissolved in water, acids will form H+(aq) ions

a compound formed when the hydrogen ions in an acid are replaced by metal ions (or other cations)

metal + acid -> salt + hydrogen • reactions between metals and acids will only occur if the metal is more reactive than hydrogen • If a metal is very reactive, the reaction may be too violent to be carried out safely

metal carbonate + acid → salt + water + carbon dioxide -neutralisation reaction

metal hydroxide + acid → salt + water -neutralisation reaction

metal oxide + acid → salt + water -neutralisation reaction

• an acid that undergoes full dissociation in water, forming its constituent ions • examples: hydrochloric acid, sulfuric acid and nitric acid

• an acid that only slightly dissociates into its constituent ions in solution • example: carboxylic acids

• some non-metal oxides react with water to produce acidic solutions • oxides of sulfur and nitrogen are involved in the production of ‘acid rain’ • carbon dioxide produces carbonic acid

• pH is a measure of H+ ion conc in aqueous solution • the higher the conc of H+ ions, the lower the pH value of the solution and the more acidic the solution • as the conc of H+(aq) ions decreases by a factor of 10, the pH value increases by one unit

• only able to donate one acidic H+ ion per acid molecule - e.g. HCl, HNO3

• can donate two acidic H+(aq) ions per acid molecule - e.g. H2SO4

• can donate three acidic H+(aq) ions per acid molecule - e.g. H3PO4

• a substance that can accept H+ ions, or has the ability to form OH−(aq) in solution • alkalis are soluble bases

• a base (alkali) which undergoes full dissociation in water, forming its constituent ions • e.g. NaOH, KOH

• a base that only partially forms ions in solution - e.g. ammonia

• soluble metal hydroxides/oxides dissolve in water to form alkaline solutions • insoluble metal hydroxides/oxides are still bases but not alkalis

acid + base -> salt + water -usually exothermic