strong and weak acids & bases

• strong acids and bases are those that completely dissociate in water
• strong acids are

  • hydrochloric acid
  • sulfuric acid
  • nitric acid
• the degree of ionisation is the ability of the non-ionised acid molecule to produce hydrogen ions
• the degree of ionisation is what determines whether and acid or strong or weak
• the more an acid molecule tends to produce hydrogen ions, the stronger it will be
• any acid, weak or strong, that is capable of donating only 1 hydrogen ion per molecule is called a monoprotic or monobasic acid
• for monoprotic acids the concentration of hydrogen ions is the same as the original concentration as all molecules have dissociated into ions
• an acid which can donate 2 hydrogen ions is called diprotic or dibasic
• for diprotic acids the hydrogen ion concentration is double the original concentration since all hydrogen ions are released in solution
• weak acids only partially dissociate in an aqueous solution
• approximately only 1% of weak acid molecules dissociate, so the concentration of hydrogen ions is much lower than the original concentration
• weak acids are

  • ethanoic acid (all carboxylic acids)
  • carbonic acid
  • sulfurous acid
• an equilibrium is set up within a weak acid which lies to the left
• any substance that reacts with an acid and accepts a proton from an acid is classified as a base
• a soluble base is called an alkali because it'll produce hydroxide ions when in an aqueous solution
• some substances act as a base but are not soluble so cant be described as an alkali
• all alkali's are bases but not all bases are alkali's
• a strong base completely dissociates in an aqueous solution
• strong bases are typically group 1 metal hydroxides
• strong bases are

  • sodium hydroxide
  • potassium hydroxide
  • calcium hydroxide
• weak bases only partially dissociate in an aqueous solution
• weak bases are

  • ammonia
  • amines
• for all acids and bases that ionise fully in solution, the [H+] and [OH-] can be determined from the initial concentration of the acid or base
• the definition of strong acid and bases is given by

  pH = -log10[H+]
• to calculate the hydrogen ion concentration from the pH the reverse calculation is used

  [H+] = 10(-pH)
• diprotic acids are :

  • sulfuric acid (H2SO4)
  • carbonic acid (H2CO3)
• monoprotic acids are:

  • hydrochloric acid (HCl)
  • acetic acid (CH3COOH)