Chemistry C7

Chemistry C7

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Alkanes

  • Chains of carbon atoms surrounded by hydrogen atoms
  • Single covalent bonds
  • Burn to give carbon dioxide and water
  • Don't react with most chemicals (Un-reactive C-C and C-H bonds)
  • Low boiling point
  • Volatile, gases at room temperature (methane and ethane)
  • Do not react with sodium
  • Insoluble in water
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Alcohols

  • -OH functional group
  • Soluble in water
  • Good solvent
  • Boiling point of 78 degrees - just below water
  • Liquid at room temperature - volatile
  • Used as solvents (can dissolve lots of compounds water can't)
  • Perfumes, aftershaves - methylated spirit (clean paint brushes, fuel)
  • Burn in air
  • Ethanol reacts with sodium to produce sodium ethoxide + hydrogen
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Carboxylic Acids

  • -COOH functional group
  • React like other acids - salts formed end in '-anoate'
  • Acid + metal -> salt + hydrogen
  • Acid + alkali (e.g. magnesium hydroxide) -> salt + water
  • Acid + carbonate -> salt + water + carbon dioxide
  • Carboxylic acids = weak acids
  • Strong tastes and smells (e.g. Vinegar = ethanoic acid)
  • ethonol +oxygen -> ethanoic acid + water (oxidation of wine or beer)
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Esters

  • Functional group -COO-
  • formed from alcohol and carboxylic acid to form ester and water
  • Esterification reaction^ - is reversible
  • Have pleasant smells, often quite sweet and fruity
  • Used in flavourings and aromas
  • Volatile - ideal for perfumes (drift to smell receptors in nose)
  • Ointments (e.g. Deep Heat smell)
  • Solvents for paint, ink, glue, or nail varnish remover
  • Plasticisers to make plastics more flexible
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Fats and Oils

  • Fats and Oils are esters of glycerol and fatty acids
  • Fat and oil molecules mostly consists of fatty acid chains
  • Can be saturated (only C-C) or unsaturated (C=C)
  • Fat - good for storing energy
  • organism can store extra energy as fat to be used later
  • ANIMAL FATS - mainly saturated, few C=C bonds, solid at room temp.
  • VEGETABLE OILS - mainly unsaturated, lots of C=C bonds, normally liquid at room temp.
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Making an Ester - Refluxing

  • Ethyl Ethanoate - ethanol needs to be reacted with ethanoic acid
  • Catalyst such as concentrated sulfuric acid can be used to speed things up
  • Or heating the mixture - bunsen burner can not be used
  • Gently heated mixture in a flask
  • Condenser to catch vapours and recycle - giving them time to react - this method is refluxing
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Making an Ester - Distillation

  • Needed to seperate ester from other stuff left in the flask (unreacted alcohol and carboxylic acid, sulfuric acid and water)
  • Mixture is heated under a fractionating column, as it boils - vapour begins to rise up the fractionating column
  • When temperature at top reaches boiling point of ethyl ethanoate - the liquid that flows out of the condenser is collected
  • This is impure ethyl ethanoate
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Making an Ester - Purification

  • Liquid collected - poured into tap funnel
  • Mixture shaken with sodium carbonate solution - removing acidic impurities
  • Ester does not mix with water, so mixture seperates into two layers - bottom layer can be tapped off (removed)
  • Remaining upper layer is then shaken with concentration calcium chloride solution to remove any ethanol. Lower layer can then be tapped off.
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Making an Ester - Drying

  • Remaining water can be removed by shaking with lumps of anhydrous (dry) calcium chloride, which absorbs it - this is called dring
  • Finally, the pure ester (pure ethyl ethanoate) can be separated from the solid calcium chloride via filtration
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Exothermic Reaction

  • Gives out energy to surroundings (mainly form of heat) and shown by rise in temperature
  • Examples inclue fuel burning, and neutrilisation reactions
  • In exothermic reactions, the products at at a lower energy than the reactants
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Endothermic Reaction

  • Takes in energy from surroundings (mainly form of heat) and shown by fall in temperature
  • An example is photosynthesis
  • In endothermic reactions the products are at a energy than the reactants
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Activation Energy

  • Minimum amount of energy needed for reaction to happen
  • If energy input is less than the activation energy there will not be enough energy to start the reaction.
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Comments

Dale McNerlin

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more cards please! :D

Former Member

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Thanks ! :)

Andrew

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cheers babe

Benjamin Atkinson

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will finish rest of module tommorow

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