GCSE AQA Chemistry 3 Organic Chemistry

GCSE AQA Chemistry 3 Organic Chemistry

1. Reversible Reactions

   • Products of reaction can react to produce original reactants
   • Reaches equilibrium in closed system
     • Amount of reactants & products reach certain balance & stay there
     • Reactions taking place at same rate
   • Temperature
     • Raise temp.
       • Endo reaction increases
     • Lower temp.
       • Exo reaction increases
   • Pressure
     • Raise pressure
       • Encourages reaction which produces less volume
     • Lower pressure
       • Encourages reaction which produces more volume
   • Catalyst
     • Reaches equilibrium faster but end up with same amount of product

2. Haber Process

   • nitrogen + hydrogen --> ammonia (+ heat)
     • Nitrogen from air - 78%
     • Hydrogen comes from natural gas/crude oil
     • Reversible reaction - reaches equilibrium
   • Industrial conditions: 200 atmospheres, 450*C, iron catalyst
   • Higher pressure favours forward reaction
     • High as possible - high % yield
   • Forward reaction - exo
     • Increasing temp. will move equilibrium wrong way - yield better at lower temp.
       • Lower temp. = lower rate of reaction
         • 450*C is a compromise
   • Iron catalyst speeds up reaction & keeps costs down

3. Alcohols

   • General Formula: Cn H2n+1 OH
   • Flammable - burn in air to produce CO2 & water
     • Dissolve completely in water --> neutral solutions
       • React with sodium to give hydrogen & alkoxides
   • Used as solvents
     • Can dissolve substances water can't dissolve
     • Ethanol - solvent for perfumes
     • Methylated spirit - ethanol, clean paint brushes, poisonous, purply-blue dye added
   • Used as fuels
     • Ethanol in spirit burners
       • Fuel for cars - renewable

4. Carboxylic Acids

   • Functional group: -COOH
   • Names end in -anoic acid'
   • React like other acids with carbonates --> CO2
     • Salts formed end in -anoate
   • Dissolve in water to produce acidic solutions
     • Ionise & release H+ ions - but don't ionise completely --> weak acidic solutions
   • Ethanoic acid dissolved in water - vinegar
   • Citric acid - fizzy drinks, get rid of scale
   • Longer chains - soaps & detergents
     • Esters
       • Ethanoic acid - v. good solvent but acidic

5. Esters

   • alcohol + carboxylic acid --> ester + water
     • Acid catalyst used
   • Functional group: -COO-
   • Have pleasant smells, volatile, flammable, dangerous, don't mix v. well with water, do mix well with alcohols
   • Used in perfumes, to make flavourings, ointments & solvents for paint, ink, glue
   • Problems...
     • Inhaling fumes irritates mucus membranes
       • Heavier than air, v. flammable
         • Some toxic - health problems with synthetic food additives?