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Question : 26
Total: 30
(a) Compare soaps and detergents on the basis of their composition and cleansing action in hard water.
(b) What happens when ethanol is treated with sodium metal ? State the behaviour of ethanol in this reaction.
(c) Draw the structure of cyclohexane.
(d) Name the following compound.
H −
−
− H
(b) What happens when ethanol is treated with sodium metal ? State the behaviour of ethanol in this reaction.
(c) Draw the structure of cyclohexane.
(d) Name the following compound.
Solution:
(a) Soaps are potassium or sodium salts of a carboxylic acid having a long aliphatic chain attached to it. They are surfactants (compounds that reduce surface tension between a liquid and another substance) so, help in the emulsification of oils in water. They are not effective in hard water and saline water. Detergents are the potassium or sodium salts of a long alkyl chain ending with a sulphonated group. They are soluble in hard water. This solubility is attributed to the fact that the sulphonated group does not attach itself to the ions present in hard water.
(b) When ethanol is treated with sodium metal, sodium ethoxide is obtained with the liberation of hydrogen gas. Sodium is an alkali metal, its standard reduction potential is low. Hence it can displace hydrogen from alcohol.
2 CH 3 − CH 2 − OH + 2 Na → 2 CH 3 − CH 2 − ONa + H 2
Ethanol acts as an oxidising agent in the reaction as :
(i) There is increase in oxidation number of sodium.
(ii) Since sodium is an electropositive element, its addition in ethanol will reduce ethanol.
(b) When ethanol is treated with sodium metal, sodium ethoxide is obtained with the liberation of hydrogen gas. Sodium is an alkali metal, its standard reduction potential is low. Hence it can displace hydrogen from alcohol.
(i) There is increase in oxidation number of sodium.
(ii) Since sodium is an electropositive element, its addition in ethanol will reduce ethanol.
(d) Acetaldehyde or Ethanal
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