Specification Point 4.32C (Paper 2C Only):
Know that ethanol can be manufactured by: reacting ethene with steam in the presence of a phosphoric acid catalyst at a temperature of about 300°c and a pressure of about 60-70 atm, the fermentation of glucose, in the absence of air, at an optimum temperature of about 30°c and using the enzymes in yeast


Ethanol (C2H5OH) is the type of alcohol found in alcoholic drinks such as wine and beer. It is also used as fuel for cars.

Manufacture of Ethanol

  1. Reacting ethene with steam (hydration):

A mixture of ethene and steam is passed over a hot catalyst of phosphoric acid at a temperature of 300°c and 60-70 atmospheres of pressure and is then condensed into a liquid for use:

Ethene with steam, Edexcel IGCSE Chemistry

Ethene   +   Water   →   Ethanol


  C2H4           H2O            C2H5OH         

Equation showing the reaction that takes place between ethene and steam                 


  1. Fermentation of glucose:

Sugar or starch is dissolved in water and yeast is added to be fermented at 30°C with the absence of oxygen for a few days. Yeast contains zymase enzymes (biological catalysts) break down starch or sugar to glucose. The yeast respires anaerobically using the glucose to form to ethanol and carbon dioxide:

 Glucose   →   Ethanol   +   Carbon Dioxide


 C6H12O6       2C2H5OH      2CO2                         

Equation showing the fermentation of glucose by anaerobic respiration

Comparing methods

Specification Point 4.33C (Paper 2C Only):
Understand the reasons for fermentation, in the absence of air, and at an optimum temperature

Fermentation: a chemical process in which microorganisms such as yeast act on carbohydrates to produce ethanol and carbon dioxide. Sugars and starch are examples of carbohydrates.

Conditions of Fermentation

Conditions of fermentation, Edexcel IGCSE Chemistry

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Author: Jamie

Jamie got a First class degree in Chemistry from Oxford University before going on to teach chemistry full time as a professional tutor. He’s put together these handy revision notes to match the Edexcel IGCSE Chemistry specification so you can learn exactly what you need to know for your exams.