Chemistry Revision Cards

- Carboxylic acids react with alcohols to make esters - Which have fruity smells

- Uses: food products, perfumes, solvents and plasticisers

- They're made by:

   1: Heating Under Reflux    2: Distillation

   3: Purification                     4: Drying

Ethanol and Ethanoic Acid are heated under reflux with presence of concentrated Sulfuric Acid.

Reflux is a process of continual evaporation and condensation.

This means the mixture is continually heated and returned to the flask.

The ester is removed by distillation.

In the distillation process, the liquid that has turned to a gas is removed from the reacting mixture.

The distillate is transferred to a Separating funnel where it is purified:

- A solution of Sodium Carbonate is added and the mixture is shaken

- It will react with any remaining acid and extract it into the aquaeous phase

- The aquaeous phase is run off

The product is transferred into a conicle flask

Anhydrous Calcium Chloride is added to the mixture

This removes any remaining water molecules

It is later removed by filtration

- Fats are esters of glycerol and fatty acids

- Living organisms make fats and oils to use as energy

- The difference between animal fats and unsaturated fats are the reactivity and bonds

     C-C                                        C=C

Unreactive                           More Reactive          

- Exothermic Reactions release energy (heat) so there is a rise in temperature

- They release energy because the products have less enerygy than the reactants did

- Endothermic Reactions are less common than Exothermic Reactions

- They take in energy so they have a temperature decrease

- Bonds need to be broken to start a chemical reaction

- Energy is needed to break bonds

- The amount of energy required to start a reaction is called the ACTIVATION ENERGY

   Hydrogen + Bromine = Hydrogen Bromide

        H2       +     Br2     =        2HBr

      434              Br-Br

      H-H      +      193  = 627 --> Activation Energy

 H-H  434

Br-Br 193

H-Br  366