4. Carbon and its Compounds Class 10 science Solutions English Medium-Exercise

NCERT Solutions Exercise 

Q1. Ethane, with the molecular formula C2H6 has

(a) 6 covalent bonds.

(b) 7 covalent bonds.

(c) 8 covalent bonds.

(d) 9 covalent bonds.

Answer: (b) 7 covalent bonds.

Q2. Butanone is a four-carbon compound with the functional group

(a) carboxylic acid.

(b) aldehyde.

(c) ketone.

(d) alcohol.

Answer: (c) ketone.

Q3. While cooking, if the bottom of the vessel is getting blackened on the outside, it means that

(a) the food is not cooked completely.

(b) the fuel is not burning completely.

(c) the fuel is wet.

(d) the fuel is burning completely. 

Answer: (b) the fuel is not burning completely.

Q4. Explain the nature of the covalent bond using the bond formation in CH₃Cl.

Answer: In CH₃Cl, three hydrogen atoms are covalently bonded to one carbon atom. Similarly, there is a covalent bond between carbon chlorine as well.

Q5. Draw the electron dot structures for

(a) ethanoic acid.

(b) H2S.

(c) propanone.

(d) F2 .

Q6. What is an homologous series? Explain with an example.

Answer: A series of carbon compounds in which a type of functional group replaces hydrogen is called a homologous series.

For example - methane (CH₂), ethane (C₂H₆), propane (C₃H₈).

There is a difference of CH₂  unit among them. The general formula of alkenes can be written as C_nH_2n and N = 2,3,4.

Q7. How can ethanol and ethanoic acid be differentiated on the basis of their physical and chemical properties?

Answer: Physical Properties :-

(i) The smell of ethanol is characteristically alcoholic while that of ethanolic acid is strong.

(ii) The melting point of ethanol is 156K while the boiling point of ethanolic acid is 290K.

(iii) The boiling point of ethanol is 351K while that of ethanolic acid is 391K.

chemical properties :-

(i) Ethanol does not affect litmus paper whereas ethanol acid turns blue litmus paper red.

(ii) Ethanol does not react with sodium carbonate while ethanol acid reacts with sodium carbonate to produce CO2 gas.

Q8. Why does micelle formation take place when soap is added to water? Will a micelle be formed in other solvents such as ethanol also?

Answer: Micelles are formed when soap is added to water because soaps have two - a long hydrocarbon tail and a negative end. The tail is water resistant and the head watery. When it reacts with a polar solvent like water, the charged part causes the hydrophilic part, so they form clumps around the heads of the soap molecules and also form froth. Ethanol is not a polar solvent so it does not form lather with soap.

Q9. Why are carbon and its compounds used as fuels for most applications?

Answer: Carbon and its compounds generate a lot of heat as a result of combustion. Their combustion is easy to control and the ignition temperature is also normal, so their compound is used as fuel.

Q10. Explain the formation of scum when hard water is treated with soap.

Answer: The calcium and magnesium ions present in hard water react with soap to form insoluble salts. Hence, a white precipitate is formed.

2C₁₇H₃₅COONa + Mg²⁺ → (C₁₇H₃₅COO)_2Mg + 2Na⁺

Q11. What change will you observe if you test soap with litmus paper (red and blue)?

Answer: Soap is alkaline in nature hence it turns red litmus paper eco blue.

Q12. What is hydrogenation? What is its industrial application?

Answer: Unsaturated hydrocarbons combine with hydrogen to form saturated compounds. This process is called hydrogenation. This process is used to make ghee from oil. Vegetable oil +H₂

Q13. Which of the following hydrocarbons undergo addition  reactions: C₂H₆ , C₃H₈ , C₃H_{6 ,} C₂H₂ and CH₄.

Answer: Addition reaction will take place in C₂H₂ and C₃H₆ because they are unsaturated hydrocarbons

Q14. Give a test that can be used to differentiate chemically between butter and cooking oil.

Answer: Butter is saturated and edible oil is unsaturated hydrocarbon. These can be differentiated with the help of bromine water. Heat butter and oil. Now put some drops of bromine water in them. There is an organic compound in butter. Similarly, when bromine is added to oil, the color of the water turns off, so it is an unsaturated hydrocarbon.

Q15. Explain the mechanism of the cleaning action of soaps.

Answer: There are two ends in the direction of soap, one is anti-water and the other is burning. The anti-water end sticks to the dirt in the clothes, but the water-resistant end sticks to the water molecules. Due to this action, froth (micelle) is formed. In this lather, the soap molecules are arranged in a circular shape. Polar part CooNa+ .