3

• Why are these acids

  Ionise when dissolved in water

  HCl (aq) —> H+(aq) + Cl-(aq)
• Alkalis are soluble in water
• Calcium hydroxide

  Ca(OH)2
• Bases are 


  Metal oxides
• Bases are insoluble in water
• pH probe is more accurate

  universal indicator can be difficult to distinguish
• Litmus paper 


  acid = red

  alkali = blue
• Methyl orange 


  Acid = red

  AlkalI= yellow
• Phenolphthalein

  Acid - colourless

  alkali- pink
• Ionisation of strong acid is irreversible
• Ionisation of weak acids reversible
• Weak acids partially ionise and dissociate into fewer H+ ions
• Weak bases only partially ionise
• All acids have to dissolve in water and ionise for acidic properties to show up
• Strong acids : ionise completely so there are more H+ ions dissolves in a solution so the pH is lower
• concentrated acid

  solution which contains a high concentration of dissolved acid molecules
• Dilute acid

  Solution which contains a low concentration of dissolved acid molecules
• Making soluble salt from insoluble base

  $H2SO4 (aq) +$$CuO(s) —> CuSo4(aq)+$$H2O(l)$
• soluble salt from insoluble base

  Place in a water bath to speed up chemical reaction
• Acid + metal carbonate —> salt + water + carbon dioxide
• Acid + metal oxide —> salt + water
• Acid + metal hydroxide —> salt + water
• Acid + metal —> salt + hydrogen
• Copper and silver don’t react with acid as they’re less reactive than hydrogen
• Group 1 aren’t reacted with acids as it’s to violent
• Displacement reaction 


  more reactive element displace less reactive element from its compound
• Titration measures exact volumes of an acid and alkali needed to react and neutralise each other
• Meniscus is a curved surface 


  read from the bottom of the meniscus
• Titre

  Recorded volume of acid required to neutralise the known volume of alkali
• Making insoluble salts 


  react two soluble salts
• To make lead chloride

  Lead nitrate is reacted with sodium chloride

  • forms lead chloride and sodium nitrate
• Insoluble salt method

  • Add the two soluble salts together
  • precipitate formed
  • filtration to capture the precipitate in filter paper
  • rinse residue (precipitate ) with distilled water to remove contamination
  • leave the filter paper containing the salt to dry in a oven or desiccator
• Making soluble salts

  • React acid with an insoluble base
  • heat acid in water bath to speed up the reaction
  • add the base in excess to ensure the solution has been neutralised
  • filter the excess reactant to obtain only salt and water
  • heat the solution to evaporate water and crystallise
• Soluble salts titration 


  Titrations used to ensure the salt isn’t contaminated with excess alkali