A food-processing company has surplus sugar solution from washing fruit. Instead of disposing of it, the company plans to make ethanol for use as a fuel add...
Question 1 Report
A food-processing company has surplus sugar solution from washing fruit. Instead of disposing of it, the company plans to make ethanol for use as a fuel additive. Fig. 1 shows the proposed route. Yeast is added only in the fermentation vessel. The purified ethanol could be blended with petrol, whereas ethanol can also be made from ethene using steam and an acid catalyst.
(a) Name the gas produced in the fermentation vessel. [1]
(b) Give the balanced chemical equation for fermentation of glucose, C6H12O6, to ethanol and the gas named in part (a). [2]
(c) Explain why the vessel is kept at a warm temperature and is not supplied with oxygen. [3]
(d) State why distillation is used after fermentation. [1]
(e) Suggest one advantage and one disadvantage of making ethanol from the fruit sugar solution rather than from ethene. [2]
Answer Details
(a) The gas is carbon dioxide. [1]
(b) \[C_6H_{12}O_6\rightarrow2C_2H_5OH+2CO_2\] [2] This balances carbon, hydrogen and oxygen atoms.
(c) A warm temperature gives yeast enzymes a suitable reaction rate. [1] Oxygen is excluded so anaerobic fermentation occurs. [1] If oxygen were present, aerobic respiration would produce carbon dioxide and water rather than ethanol. [1]
(d) Distillation is used to separate and obtain ethanol from the aqueous fermentation mixture. [1]
(e) An advantage is that this route uses renewable plant material or a waste sugar solution. [1] A disadvantage is that fermentation is slower than reacting ethene with steam. [1] Dependence on crops/land or seasonal supply is also acceptable.
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