CHAPTER. 4
Carbon and Its Compounds
Objective Questions
Multiple Choice Questions
- Carbon exist in atmosphere in the form of
(a) Carbon monoxide only
(b) Carbon dioxide only
(c) Carbon monoxide in traces and carbon dioxide
(d) Coal.
- Carbon is a
(a) monovalent
(b) bivalent
(c) trivalent
(d) tetravalent
- Ethane with the molecular formula C₂H6 has
(a) 6 covalent bonds (c) 8 covalent bonds
(b) 7 covalent bonds (d) 9 covalent bonds.
- 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.
- Which one of the following is an unsaturated hydrocarbon?
(a) Butane
(b) Propane
(c) Acetylene
(d) Decane.
- The gas used in welding and cutting metals is
(a) ethyne
(b) ethane
(c) ethene
(d) propene.
- Major constituent of LPG is
(a) ethene
(b) propane
(c) pentane
(d) butane.
- Buckminster fullerene is an example of ………. of carbon.
(a) an isomer
(b) an allotrope
- c) an isotope
(d) a functional group.
- Complete combustion of a hydrocarbon gives
(a) CO + H₂O
(b) CO₂ + H2₂
(c) CO₂ + H₂O
(d) CO + H₂
- Which of the following represents alkynes?
(a)-C-C-
(b)-C=C-
(c) —C=C-
(d) None of these.
- General formula of alkyne is
(c) Caca
(d) None of these.
(a) C₂H₂-2 (c) C₂H₂
(b) CnH2n+2 (d) C₂H,
- Covalent compounds generally
(a) are soluble in water
(c) hydrolize in water
(b) ionize in water
(d) are insoluble in water.
- The soap molecule has a
(a) hydrophilic head and a hydrophobic tail
(b) hydrophobic head and hydrophilic tail
(c) hydropholic head and hydrophobic tail
(d) hydrophibic head and hydrophilic tail.
- In the soap micelles
(a) The ionic end of soap is on the surface of the cluster and the carbon chain is the interior of the cluster
(b) The ionic end of the soap is in the interior of the cluster and the carbon chain is out of the cluster
(c) Both ionic end and carbon chain are in the interior of the cluster
(d) Both ionic end and carbon chain are the exterior of the cluster.
Ans. 1. (c), 2. (d), 3. (b), 4. (b), 5. (c), 6. (a), 7. (d), 8. (b), 9. (c),
- (a), 12. (d), 13. (a), 14. (b).
Fill in the Blanks
- Compounds of carbon having double and triple bonds between their carbon atomsare called…………….
- The valency of carbon is……………
- The compounds having carbon hydrogen are called…………
- Hydrocarbon having only single bonds are called…………..
Ans. 1. unsaturated compounds, 2. 4, 3. hydrocarbon, 4. Saturated hydrocarbon.
True/False
- The general formula C,H₂,, is valid for any alkene with any number of multiple bonds.
- General formula of alkanes is C,H₂n+2
- Covalent compounds have low melting and boiling points as compared to ionic compounds.
Ans. 1. False, 2. True, 3. True.
Match the Columns
Column ‘A’. Column ‘B’
- Ethane. (a) Allotrope of carbon
- Diamond). (b) Friedrich Wohler
- Urea. (c) C₂H6
Ans. 1.→ (c), 2. (a), 3. (b).
Answer in one Word/Sentence
- Why are unsaturated hydrocarbons more reactive than saturated hydrocarbons?
Ans. Because of presence of double and triple bonds in unsaturated hydrocarbons.
- What is the common name for ethyne?
Ans. Acetylene.
- Name the type of hydrocarbon taking part in addition reaction.
Ans. Unsaturated hydrocarbon.
Very Short Answer Type Questions
- 1. What would be the electron dot structure of carbon dioxide which CO₂ ?
Ans. Electron dot structure of CO₂ is:has formala
- 2. What would be the electron dot structure of the molecule of sulphur which is made up eight atoms of sulphur?
Ans. Electron dot structure of a sulphur molecule :
- 3. What change will you observe if you test soap with litmus paper (red and blue)!
Ans. Since soap is basic in nature, it will turn red litmus blue. However, the colour of blue litmus will remain blue.
- 4. Which of the following hydrocarbons undergo addition reactions ?
C₂H6, C3Hg, C3H6, C₂H₂ and CH4.
Ans. Unsaturated hydrocarbons undergo addition reactions. Being unsaturated hydrocarbons, C3H6 and C₂H₂ will undergo addition reactions.
- 5. What are saturated hydrocarbons?
Ans. The hydrocarbons in which valency of carbon is satisfied by a single covalent bond are called saturated hydrocarbons. Alkanes like methane (CH₂), ethane (C₂H₂) etc. are examples of saturated hydrocarbons.
- 6. Would you be able to check if water is hard by using a detergent?
Ans. Detergent gives lather with hard and soft water both, while a soap gives lather with soft water only. Thus, it is not possible to check if water is hard by using a detergent
- 7. Define the covalent bonds.
Ans. Covalent bonds: The bond formed by sharing a pair of valency electron between two atoms is called the covalent bond and the compound so formed are called covalent compounds.
- 8. Write the two names of carbon allotropes.
Ans. (i) Graphite, (ii) Diamond.
Short Answer Type Questions
- 1. Why are carbon and its compounds used as fuels for most applications?
Ans. Carbon and its compounds give large amount of heat on combustion due to high percentage of carbon and hydrogen. Carbon compounds used as fuel have optimum ignition temperature with high calorific values and are easy to handle. Their combustion can be controlled. Therefore, they are used as fuels.
- 2. Explain the formation of scum when hard water is treated with soap.
Ans. Hard water often contains salts of calcium and magnesium, Soap molecules react with the salts of calcium and magnesium and form a precipitate. This precipitate begins floating or an off white layer over water. This layer is called scum. Sopas lose their cleansing property in hard water because of the formation of scum.
- 3. People use a variety of methods to wash clothes. Why is agitation necessary to clean clothes?
Ans. A soap molecule has two parts, namely, hydrophobic and hydrophilic. With the help of these, it attaches to the grease and dirt particles and forms a cluster called micelle. These micelles remain suspended as a colloid. To remove these micelles, it is necessary to
agitate clothes.
- 4. Explain the nature of the covalent bond using the bond formation in CH₂CI.
Ans. The structure of CH₂Cl is given below:
Carbon has four valence electrons. It shares I electron each with 3 hydrogen atoms and 1 electron with chlorine. The bond between C and Cl atoms is covalent, but due to high electronegativity of Cl, the C-Cl bond is polar in nature.
- 5. What are the two properties of carbon which lead to a huge number of carbon compounds we see around us?
Ans. The two properties of carbon which lead to a large number of compounds are
Catenation-It is the ability to form bonds with other atoms of carbon.
Tetravalency-With the valency of four, carbon is capable of forming bonds with four other atoms.
- 6. Write the names, formula and structural formula of first four hydrocarbons.
Ans. Name, formula and structural formula of Hydrocarbon:
Long Answer Type / Analytical Questions
- 1. Why does micelle formation take place when soap is added to water? Will a micelle be formed in other solvents such as ethanol also?
Ans. Soap molecule has two ends. One end is hydrophillic and another end is hydrophobic. When soap is dissolved in water and clothes are put in the soapy solution, soap molecules converge in a typical fashion to make a structure, called micelle. The hydrophobic ends of different molecules surround a particle of grease and make the micelle, which is a spherical structure. In this, the hydrophillic end is outside the sphere and hydrophobic end is towards the centre of the sphere. This is why micelle formation takes place when soap is added to water.
Since ethanol is not as polar as soap, so micelles will not be formed in other solvents like ethanol.
- 2. Explain the mechanism of the cleansing action of soaps.
Ans. The dirt present on clothes is organic in nature and insoluble in water. Therefore, it cannot be removed by only washing with water. When soap is dissolved in water, its hydrophobic ends attach themselves to the dirt and remove it from the cloth. Then the molecules of soap arrange themselves in micelle formation and trap the dirt at the centre of the cluster. These micelles remain suspended in the water. Hence the dirt particles are easily rinsed away
- 3. Draw the electron dot structure of the following: (1) CH4 (2021), (ii) CO₂
Ans. (1) Electron dot structure of CH₂ is:
- 4. Write any two differences between soap and detergent.
Ans. Differences between soap and detergent are as follows:
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