GCSE AQA Chemistry 2 Salts & Electrolysis

GCSE AQA Chemistry 2 Salts & Electrolysis

1. Acids & Alkalis

   • Acid: substance with pH less than 7, form H+ ions in water
   • Base: substance with pH greater than 7
     • Alkali: base that dissolves in water, form OH- ions in water
   • Neutralisation: acid + base --> salt + water
   • Acids & metals
     • Acid + metal (oxide/hydroxide) --> salt + hydrogen
   • Ammonia
     • Dissolves in water --> alkaline solution
     • Ammonia + Nitric acid --> Ammonium nitrate
       • Ammonium nitrate - good fertiliser, has nitrogen from 2 sources, plants need nitrogen to make proteins

2. Making salts

   • Making soluble salts using a metal/insoluble base
     • Filter out excess, evaporate & crystallise
   • Making soluble salts using an alkali
     • Neutralise, repeat to remove indicator, evaporate & cystallise
   • Making insoluble salts - precipitation reactions
     • Filter salt out, wash & dry

3. Electrolysis

   • Splitting up with electricity - requires electrolyte
     • Contains free electrons - conduct electricity
     • Needs flow of electrons, electrons taken away at +ve electrode & given to other ions at -ve electrode
   • Oxidation & reduction
     • Oxidation Is Loss of electrons
     • Reduction Is Gain of electrons
   • Reactivity affects products formed
     • At -ve electrode - if metal ions & H+ ions present, metal ions will stay in solution if metal is more reactive than hydrogen - keener to stay as ions
       • At +ve electrode - if OH- & halide ions are present, molecules of chlorine formed, if no halide, oxygen formed
   • Electrolysis of Sodium Chloride solution produces...
     • Hydrogen
     • Chlorine
       • Bleach & plastics
     • Sodium hydroxide
       • Soap
   • Extraction of aluminium
     • Cryolite lowers temp, & costs
     • Electrodes made of carbon - CO2 - 'eaten away'
     • Aluminium forms at -ve electrode Oxygen forms at +ve electrode
   • Electroplating
     • At -ve electrode - metal object you want to plate
       • At +ve electrode - pure metal