OCR A Jan 2011 Paper 2 Q7

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7 Biofuels such as bioethanol and biodiesel are increasingly being used as an alternative to fossil fuels to provide energy. (a) Describe, with the aid of an equation, how bioethanol is manufactured by fermentation. 21[3] (b) Biodiesel is obtained from plant oils. The manufacture involves several stages, all of which have a high energy requirement. Biodiesel is often described as being carbon-neutral because:plants convert atmospheric carbon dioxide into carbon compounds on burning biodiesel this carbon dioxide is returned to the atmosphere. (i) Construct an equation to show the complete combustion of biodiesel. Assume that the molecular formula of the biodiesel is C15H30O2.[2] (ii) Suggest why biodiesel is not completely carbon-neutral.[1] (c) Many scientists suggest that society should use more biofuels rather than fossil fuels to provide energy. Other scientists are worried that biofuels will need large areas of land to grow suitable crops. Suggest disadvantages or advantages, other than being carbon-neutral, of using more biofuels.[3]OCR 2011 Turn over<br /> (d) Unsaturated compounds in plant oils can also be used to make margarine. 22 Describe how.[2] (e) Part of the structure of an unsaturated compound in plant oils is shown below: (i) Draw the displayed formula of the Z isomer of this part of the structure. CH2CH2CH=CHCH2CH2 (ii) Explain why this part of the structure can have an E and a Z isomer. [1][2] [Total: 14] END OF QUESTION PAPEROCR 2011<br />

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