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Alcohols – Revision Pack (C6) The formula of ethanol: The molecular formula for ethanol is C 2 H 5 OH – ethanol is made using the process of fermentation: Glucose Ethanol + Carbon Dioxide C 6 H 12 O 6 2C 2 H 5 OH + 2CO 2 Ethanol is made by the fermentation of a glucose solution: - The reaction is catalysed (sped up) by the enzymes in yeast This ONLY happens in the absence of oxygen The dilute liquid made then undergoes fractional distillation to produce ethanol There’s more than one alcohol? The alcohols are a group of compounds which have the general formula C n H 2n+1 OH Alcohol Methanol Molecular Formula CH 3 OH Ethanol C 2 H 5 OH Propanol C 3 H 7 OH Butanol C 4 H 9 OH Pentanol C 5 H 11 OH Displayed Formula The table above shows the molecular and displayed formula of alcohols with one to five hydrocarbons (there are MANY more) – REMEMBER these! Only ethanol is made using fermentation, using very specific conditions: 1) If the temperature is too low, the enzymes in the yeast are inactive 2) If the temperature is too high, the enzymes in the yeast are denatured 3) If air somehow gets in, ethanol is not made – ethanoic acid is by a different reaction Alcohols – Revision Pack (C6) Ethanol from Ethene: Ethanol made using fermentation can also be used as a fuel. This is a renewable fuel because the plants that make the sugar (glucose) for the process can be grown VERY quickly. Ethanol that is used in industry can also be made from ethene. Ethanol made in this way is NON-renewable. This is because the ethene it is made from comes from fossil fuels. These fossil fuels CANNOT be replaced and are a finite (limited) resource. The reaction used to make ethanol from ethene is called hydration because water is added to the ethene molecule: Ethene + Water Ethanol C 2 H 4 + H 2 O C 2 H 5 OH A hot phosphoric acid catalyst is used in this reaction; ethene and steam are passed over it. Advantages and Disadvantages of Ethanol Production: Processing By Fermentation 35oC – LESS energy needed Batch (disadvantage) By Hydration Hot catalyst – MORE energy needed Continuous (advantage) Sustainability Sustainable (advantage) Purification Fractional Distillation needed (disadvantage) Low (disadvantage) From a finite resource (disadvantage) Fairly pure on production (advantage) High (disadvantage) Conditions Percentage Yield / Atom Economy Alcohols – Revision Pack (C6) Past Papers: PPQ(1): Alcohols – Revision Pack (C6) PPQ(2): Alcohols – Revision Pack (C6) PPQ(3): PPQ(4): Continued on next page... Alcohols – Revision Pack (C6) PPQ(5): Alcohols – Revision Pack (C6) PPQ(6): \ Alcohols – Revision Pack (C6) Mark Schemes: PPQ(1): PPQ(2): Alcohols – Revision Pack (C6) PPQ(3): PPQ(4): PPQ(5): PPQ(6):