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Question : 12
Total: 12
(a) (i) What are isomers? Write the structures of two compounds having molecular formula C 3 H 6 O
(ii) What are soaps? How are they chemically different from detergents? Why do soaps not work effectively in hard water?
OR
(b) (i) What is a homologous series of carbon compounds? Write general formula for alkynes. Name and draw the electron dot structure of first homologue of this series.
(ii) State the meaning of the functional group in an organic compound. Write the formula of the functional group present in alcohols and carboxylic acids.
(ii) What are soaps? How are they chemically different from detergents? Why do soaps not work effectively in hard water?
OR
(b) (i) What is a homologous series of carbon compounds? Write general formula for alkynes. Name and draw the electron dot structure of first homologue of this series.
(ii) State the meaning of the functional group in an organic compound. Write the formula of the functional group present in alcohols and carboxylic acids.
Solution:
(a) (i) Chemical compounds that have identical chemical formulae but differ in properties and the arrangement of atoms in the molecule are called isomers.
The isomers ofC 3 H 6 O
Soap is potassium or sodium salt of a carboxylic acid attached to a long aliphatic chain. Detergent is the potassium or sodium salts of a long alkyl chain ending with a sulphate group.
Hard water contains calcium and magnesium ions. When soaps are dissolved in hard water, these ions displace sodium or potassium from their salts and form insoluble calcium or magnesium salts of fatty acids. These insoluble salts separate as scum. This is the reason why soap do not work in hard water.
OR
(b) (i) A homologous series is a collection of compounds with the same general formula that differ only in the carbon chain length. Compounds in a homologous series often have a fixed set of functional groups, resulting in chemical and physical properties that are comparable.
Alkynes are hydrocarbons which contain carbon-carbon triple bonds. Their general formula isC n H 2 n − 2
Ethyne is the first member of alkyne homologous series. Its structure is: Electron-dot structure:
Formula of functional groups:
Carboxylic acid:− COOH
Alcohol:− OH
The isomers of
(ii) A soap is a water-soluble compound which is made via a process called saponification by the reaction between sodium hydroxide or potassium hydroxide with vegetable or animal oil (fats).
Soap is potassium or sodium salt of a carboxylic acid attached to a long aliphatic chain. Detergent is the potassium or sodium salts of a long alkyl chain ending with a sulphate group.
Hard water contains calcium and magnesium ions. When soaps are dissolved in hard water, these ions displace sodium or potassium from their salts and form insoluble calcium or magnesium salts of fatty acids. These insoluble salts separate as scum. This is the reason why soap do not work in hard water.
OR
(b) (i) A homologous series is a collection of compounds with the same general formula that differ only in the carbon chain length. Compounds in a homologous series often have a fixed set of functional groups, resulting in chemical and physical properties that are comparable.
Alkynes are hydrocarbons which contain carbon-carbon triple bonds. Their general formula is
Ethyne is the first member of alkyne homologous series. Its structure is: Electron-dot structure:
(ii) A functional group is defined as an atom or a group of atoms that gives some characteristic properties to an organic compound. A functional group is attached to the carbon chain through its free valency or valencies. It acts as the reactive side of the molecule.
Formula of functional groups:
Carboxylic acid:
Alcohol:
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