Chemistry Revision Cards

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  • Created by: babeyshep
  • Created on: 21-04-15 12:29

Esters

- 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

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Process One: Heating Under Reflux

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.

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Process Two: Distillation

The ester is removed by distillation.

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

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Process three: Purification

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

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Process Four: Drying

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

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Fats

- 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          

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Exothermic Reaction

- 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

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Endothermic Reaction

- Endothermic Reactions are less common than Exothermic Reactions

- They take in energy so they have a temperature decrease

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Activation Energy

- 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

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Hydrogen & Bromine

   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

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