Carbon and Its Compounds
NCERT Exemplar Problems
Long Answer Part 1
What are hydrocarbons? Give examples.
Answer: Those compounds which are made up of carbon and hydrogen are called hydrocarbons. Methane and ethane are examples of hydrocarbons.
Give the structural differences between saturated and unsaturated hydrocarbons with two examples each.
Answer: All the bonds are single bonds in a saturated hydrocarbon. But one of the bonds is either a double or a triple bond in an unsaturated hydrocarbon. Methane and ethane are examples of saturated hydrocarbon. Ethene and ethyne are examples of unsaturated hydrocarbons.
What is a functional group? Give examples of four different functional groups.
Answer: A particular atom or a radical is responsible for the specific property of an organic compound. This atom or radical is called the functional group of that organic compound. Examples of functional group are: Hydroxyl group ( - OH), Aldehyde ( - CHO), Ketone ( - CO) and carboxylic group ( - COOH).
A salt X is formed and a gas is evolved when ethanoic acid reacts with sodium hydrogencarbonate. Name the salt X and the gas evolved. Describe an activity and draw the diagram of the apparatus to prove that the evolved gas is the one which you have named. Also, write chemical equation of the reaction involved.
Answer: Salt X is sodium ethanoate and the evolved gas is carbon dioxide.
Figure Ref: NCERT Science Book Class 10
We know that when carbon dioxide is passed through lime water; the lime water turns milky. This is taken as the confirmatory test for evolution of carbon dioxide. For this, following activity can be done.
Activity: Take a test tube and a bent tube. Take ethanoic acid and sodium bicarbonate solution in the test tube. Insert the bent tube in the cork and fit the cork at the mouth of the test tube. Fill lime water in the bent tube so that lime water is in the ‘U’ portion of this tube.
After some time; it is observed that the lime water turns milky. This confirms that the evolved gas is carbon dioxide.
This reaction can be shown by following equation.
CH2COOH + NaHCO3 → CH3COONa + H2O + CO2CH2COOH + NaHCO2→ CH3COONa + H2O + CO2
Name the reaction which is commonly used in the conversion of vegetable oils to fats. Explain the reaction involved in detail.
Answer: The reaction which is commonly used in the conversion of vegetable oils to fats is called hydrogenation reaction. During this reaction, hydrogen is added to unsaturated hydrocarbon. This is an addition reaction which takes place in the presence of catalyst; like palladium or nickel. Addition of hydrogen leads to conversion of unsaturated hydrocarbon to saturated hydrocarbon. This can be shown by following equation.
Write the formula and draw electron dot structure of carbon tetrachloride.
Answer: Carbon tetrachloride: CCl4.
What is saponification? Write the reaction involved in this process.
Answer: When an ester is treated with a base, the ensuing reaction produces carboxylic acid and ethanol. This reaction is called saponification reaction. This can be shown by following equation.
CH2COOC2H5 + NaOH → CH3 COONa + C2H5OH
Esters are sweet-smelling substances and are used in making perfumes. Suggest some activity and the reaction involved for the preparation of an ester with well labeled diagram.
Answer: Take a test tube and put 1 ml ethanol and 1 ml glacial acetic acid in it. Put a few drops of concentrated sulphuric acid in the test tube as well.
- Now, heat the test tube in a water bath at about 60°C; for about 15 minutes.
- After finishing the heating; empty the contents of the test tube into a beaker which is filled with about 50 ml water.
- The mixture; thus obtained; smells sweet. This shows the formation of ester.
- This reaction can be shown by following equation.
CH3COOH + CH3CH2OH + Conc. H2SO4 → CH3COOCH2CH3 + H2O