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Class 10 Science Chapter 4 Question Answers - Carbon and its compounds

Q1: Explain the concept of catenation in carbon and its role in forming a vast number of compounds. Provide examples of catenation and write the structural formula for ethyne (C₂H₂), highlighting its triple bond.
Ans: 
Catenation refers to the unique property of carbon atoms to form strong covalent bonds with other carbon atoms, leading to the formation of long chains, branched chains, and rings. This property is the foundation for the diversity and complexity of carbon compounds, also known as organic compounds.
Role of Catenation: Catenation allows carbon to create a wide variety of molecules with different sizes, shapes, and properties. It is the key reason for the existence of numerous organic compounds in nature.
Examples of Catenation:

  • Hydrocarbons: Alkanes, alkenes, and alkynes are examples of hydrocarbons formed through catenation. For instance, ethane (C₂H₆) has a single bond between two carbon atoms, ethene (C₂H₄) has a double bond, and ethyne (C₂H₂) has a triple bond.
  • Aliphatic Chains: Long aliphatic chains, such as in fatty acids and hydrocarbons, are created due to catenation.
  • Aromatic Compounds: Benzene (C₆H₆) and other aromatic compounds exhibit catenation, forming a stable hexagonal ring of carbon atoms.

Structural Formula for Ethyne:
H-C≡C-H
In the structural formula for ethyne, the triple bond between the two carbon atoms is represented by the triple dash (≡).

Q2: Describe the process of the soap formation reaction known as saponification. Explain how soap molecules remove dirt and grease from clothes during washing. Write the balanced chemical equation for the saponification of a triglyceride (fat) with sodium hydroxide (NaOH).
Ans: 
Saponification is a chemical process that involves the hydrolysis (splitting) of fats and oils (triglycerides) in the presence of a strong base, usually sodium hydroxide (NaOH), to produce soap and glycerol.
Process of Saponification: In saponification, three fatty acid molecules from the triglyceride react with three sodium hydroxide molecules, releasing glycerol and forming soap molecules. The soap molecules have a hydrophilic (water-attracting) head and a hydrophobic (water-repelling) tail.
Action of Soap Molecules: The hydrophobic tails of soap molecules surround dirt and grease particles, while the hydrophilic heads face outwards. When the clothes are agitated in water, the soap molecules form micelles, trapping the dirt and grease in their centers. These micelles are then rinsed away, along with the trapped dirt, when the clothes are rinsed with water.
Balanced Chemical Equation for Saponification:
3CH₃(CH₂)₁₄COOCH₂CH(OOC(CH₃)₃)₂ + 3NaOH → CH₂(OH)CH(OOC(CH₃)₃)₂ + 3CH₃(CH₂)₁₄COONa
Triglyceride + Sodium Hydroxide → Glycerol + Soap

Q3: Explain the difference between saturated and unsaturated hydrocarbons. Provide examples of each, and write the structural formula for but-2-ene, an unsaturated hydrocarbon.
Ans: 
Saturated and unsaturated hydrocarbons differ based on the types of carbon-carbon bonds present in their molecular structures.
Saturated Hydrocarbons: Saturated hydrocarbons have only single carbon-carbon bonds. They are fully "saturated" with hydrogen atoms. Alkanes are an example of saturated hydrocarbons. For instance, methane (CH₄) and ethane (C₂H₆) are saturated hydrocarbons.
Unsaturated Hydrocarbons: Unsaturated hydrocarbons have one or more multiple carbon-carbon bonds (double or triple bonds) in their structures. They are "unsaturated" with hydrogen atoms. Alkenes and alkynes are examples of unsaturated hydrocarbons. Ethene (C₂H₄) is an example of an unsaturated hydrocarbon with a double bond.
Structural Formula for But-2-ene:
H₂C=CH-CH₂-CH₃
In the structural formula for but-2-ene, the double bond between the two carbon atoms is represented by the double dash (=).

Q4: Discuss the harmful effects of carbon monoxide (CO) on human health. Explain how carbon monoxide is formed during incomplete combustion and why it is known as a "silent killer." Write the balanced chemical equation for the combustion of carbon in limited oxygen to form carbon monoxide.
Ans: 
Harmful Effects of Carbon Monoxide: Carbon monoxide is a colorless, odorless, and tasteless gas that poses serious health risks. When inhaled, it binds to hemoglobin in the blood, preventing the transport of oxygen, leading to oxygen deprivation and potential tissue damage. Symptoms of carbon monoxide poisoning include headaches, dizziness, nausea, confusion, and even death.
Formation during Incomplete Combustion: Carbon monoxide is produced when carbon-containing fuels, such as coal, wood, and gasoline, undergo incomplete combustion due to insufficient oxygen. Incomplete combustion occurs when there is limited oxygen available for the fuel to burn completely.
"Silent Killer": Carbon monoxide is known as a "silent killer" because its presence is difficult to detect without proper equipment. It lacks the characteristic odor associated with other harmful gases, making it particularly dangerous as it can go unnoticed.
Balanced Chemical Equation for Formation of Carbon Monoxide:
2C + O₂ → 2CO
Carbon + Oxygen → Carbon Monoxide
In this reaction, carbon reacts with limited oxygen to form carbon monoxide. The incomplete combustion of carbon-based fuels can lead to the release of carbon monoxide into the environment.

Q5: Explain the concept of covalent bonding and provide an example of a covalent compound. Describe the difference between polar and non-polar covalent bonds. Write the chemical formula for hydrogen chloride (HCl) and carbon tetrachloride (CCl₄), indicating the type of covalent bond in each compound.
Ans: 
Covalent bonding is a type of chemical bonding in which atoms share electrons to achieve a stable electron configuration. This results in the formation of molecules held together by covalent bonds.
Example of Covalent Compound: Methane (CH₄) is an example of a covalent compound. It is formed when one carbon atom shares electrons with four hydrogen atoms.
Polar and Non-Polar Covalent Bonds: Polar covalent bonds occur when atoms with different electronegativities share electrons. Electronegativity is the ability of an atom to attract electrons. In polar covalent bonds, the shared electrons are pulled closer to the more electronegative atom, resulting in partial charges (δ⁺ and δ⁻) on the atoms. Non-polar covalent bonds occur when atoms with similar electric

Q6: Explain the formation of a covalent bond using the concept of overlapping atomic orbitals. Describe the formation of a sigma (σ) bond and a pi (π) bond in a double bond. Provide an example of a molecule containing a double bond and draw its Lewis structure.
Ans: 
A covalent bond is formed when two atoms share electrons to achieve a stable electron configuration. This sharing involves the overlapping of their atomic orbitals.
Formation of Sigma (σ) and Pi (π) Bonds: In a single covalent bond, a sigma (σ) bond is formed when two atomic orbitals overlap head-to-head, allowing for the sharing of electrons along the bond axis. In a double bond, there is a sigma bond and a pi (π) bond. A pi bond is formed when two parallel p orbitals overlap sideways, resulting in the sharing of electrons above and below the bond axis.
Example of Molecule with a Double Bond: Ethene (C₂H₄)
Lewis Structure:
H
|
C = C
|
H
In ethene, the carbon-carbon double bond consists of one sigma (σ) bond and one pi (π) bond. The sigma bond is formed by the head-to-head overlap of the carbon atomic orbitals, while the pi bond is formed by the sideways overlap of the p orbitals.

Q7: Explain the concept of isomerism in organic compounds. Provide examples of structural and functional isomerism, and write the structural formula for butanol (C₄H₉OH), indicating its isomeric form.
Ans: 
Isomerism is a phenomenon in which two or more compounds have the same molecular formula but different structural arrangements or spatial orientations, resulting in distinct properties.
Structural Isomerism: Structural isomers have the same molecular formula but different connectivity of atoms. For example, pentane (C₅H₁₂) has three structural isomers: n-pentane, isopentane, and neopentane.
Functional Isomerism: Functional isomers have the same molecular formula but different functional groups. For instance, butanal and butanone are functional isomers of butane (C₄H₁₀O).
Structural Formula for Butanol (C₄H₉OH):
H H H H
| | | |
H-C-C-C-C-OH
| | | |
H H H H
Butanol has two isomeric forms: n-butanol (1-butanol) and iso-butanol (2-methyl-1-propanol). The structural arrangement of the carbon atoms is different in these isomers.

Q8: Explain the concept of homologous series in organic chemistry. Describe how members of a homologous series are related and provide examples. Write the molecular formula for the next member of the alkane homologous series after heptane (C₇H₁₆).
Ans: 
A homologous series in organic chemistry refers to a group of organic compounds that have the same functional group and exhibit a gradual increase in molecular structure and properties. Members of a homologous series share a common general formula.
Relation among Members of a Homologous Series: Members of a homologous series have a constant difference in the number of carbon and hydrogen atoms between consecutive compounds. They exhibit similar chemical properties due to the same functional group, while physical properties (such as boiling points and melting points) change gradually as the molecular size increases.
Examples of Homologous Series: Alkanes, Alkenes, Alcohols
Molecular Formula for the Next Member after Heptane (C₇H₁₆): Octane (C₈H₁₈)

Q9: Discuss the role of carbon in the diversity of organic compounds. Explain how the presence of different functional groups leads to the formation of a wide variety of organic compounds. Provide examples of functional groups and their properties.
Ans:
Carbon's ability to form covalent bonds with other carbon atoms and different elements is central to the diversity of organic compounds. The presence of various functional groups, which are specific arrangements of atoms that give a compound its characteristic properties, contributes to the wide range of organic molecules.
Role of Functional Groups in Diversity: Functional groups determine the chemical behavior and properties of organic compounds. Different functional groups can be added to a carbon skeleton to create new compounds with distinct characteristics.
Examples of Functional Groups and Properties:

  • Hydroxyl (OH): Present in alcohols, imparts polarity and the ability to form hydrogen bonds.
  • Carbonyl (C=O): Present in aldehydes and ketones, affects reactivity and solubility.
  • Carboxyl (COOH): Present in carboxylic acids, contributes to acidity and reactivity.
  • Amino (NH₂): Present in amines, plays a role in base properties and hydrogen bonding.
  • Phenyl (C₆H₅): Present in aromatic compounds, influences stability and reactivity.

The diversity of functional groups allows for the creation of a vast array of organic compounds with varying chemical properties and applications.

Q10: Explain the process of fermentation as a method for the production of ethanol. Describe the raw materials, enzymes, and conditions required for fermentation. Write the balanced chemical equation for the fermentation of glucose to ethanol.
Ans: 
Fermentation is a biological process in which microorganisms, such as yeast, convert sugars into alcohol and carbon dioxide in the absence of oxygen. It is commonly used in the production of ethanol, a valuable fuel and industrial chemical.
Process of Fermentation for Ethanol Production:

  • Raw Materials: The main raw material for fermentation is a carbohydrate source, such as glucose from sugarcane or starch from grains.
  • Enzymes: Yeast cells contain enzymes, primarily zymase, which catalyze the conversion of sugars to ethanol and carbon dioxide.
  • Conditions: Fermentation occurs under anaerobic (absence of oxygen) conditions, at a moderate temperature (around 25-35°C) and slightly acidic pH.

Balanced Chemical Equation for Fermentation of Glucose to Ethanol:
C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂
Glucose → Ethanol + Carbon Dioxide
In this reaction, glucose is converted by yeast into ethanol and carbon dioxide. The process of fermentation is essential for producing alcoholic beverages, biofuels, and other industrial products.

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