of this mixture, pure alcohol ( %) is obtained. This is called absolute alcohol . More to know Yeast and Fermentation: Yeasts are single–celled microorganisms, belonging to the class of fungi. The enzymes present in yeasts catalyse many complex organic reactions.
Fermentation is conversion of complex organic molecules into simpler molecules by the action of enzymes. E.g. Curdling of milk . .
Physical properties i) Ethanol is a colourless liquid, having a pleasant smell and a burning taste. ii) It is a volatile liquid. Its boiling point is C (351K), which is much higher than that of its corresponding alkane, i.e. ethane (Boiling Point = K).
iii) It is completely miscible with water in all proportions. . . Chemical Properties (i) Dehydration (Loss of water) When ethanol is heated with con H SO at 443K, it loses a water molecule i.e.
dehydrated to form ethene. CH CH OH CH = CH + H O Ethanol Ethene (ii) Reaction with sodium: Ethanol reacts with sodium metal to form sodium ethoxide and hydrogen gas. 2C H OH + 2Na 2C H ONa + H ↑ sodium ethoxide 443K Conc.H SO (iii) Oxidation: Ethanol is oxidized to ethanoic acid with alkaline KMnO or acidified K Cr O CH CH OH CH COOH +H O [O] Ethanoic acid During this reaction, the orange colour of K Cr O changes to green. Therefore, this reaction can be used for the identification of alcohols.
(iv) Esterification: The reaction of an alcohol with a carboxylic acid gives a compound having fruity odour. This compound is called an ester and the reaction is called esterification. Ethanol reacts with ethanoic acid in the presence of conc. H SO to form ethyl ethanoate, an ester.
C H OH + CH COOH CH COOC H + H O Ethanol Ethanoic acid Ethyl ethanoate conc.H SO (v) Dehydrogenation: When the vapour of ethanol is passed over heated