Chapter 9: Carbon Compounds
Solved textbook questions with step-by-step explanations.
ScienceSpark
Grade 10 Q&A: Chapter 9: Carbon Compounds
Concept Questions
Q1: Why is carbon called a 'versatile element'?
Answer: Carbon is called a 'versatile element' because it can form a very large number of compounds due to its unique properties of catenation (self-linking) and tetravalency (valency of 4).
Q2: What is 'catenation'?
Answer: Catenation is the unique property of carbon atoms to link with other carbon atoms through covalent bonds to form long chains, branched chains, or closed rings.
Q3: What is the valency of carbon?
Answer: The valency of carbon is 4 (tetravalency).
Q4: What are 'hydrocarbons'?
Answer: Hydrocarbons are organic compounds composed solely of carbon and hydrogen atoms.
Q5: Name the three types of hydrocarbons based on their carbon-carbon bonds.
Answer: The three types of hydrocarbons are alkanes (single bonds), alkenes (at least one double bond), and alkynes (at least one triple bond).
Q6: What is a 'saturated hydrocarbon'? Give an example.
Answer: A saturated hydrocarbon is a hydrocarbon in which all carbon-carbon bonds are single bonds, meaning each carbon atom is bonded to the maximum number of hydrogen atoms possible. Example: Methane (CH₄) or Ethane (C₂H₆).
Q7: What is an 'unsaturated hydrocarbon'? Give an example.
Answer: An unsaturated hydrocarbon is a hydrocarbon that contains at least one carbon-carbon double bond or triple bond. Example: Ethene (C₂H₄) or Ethyne (C₂H₂).
Q8: What is a 'functional group'?
Answer: A functional group is an atom or a group of atoms that is responsible for the characteristic chemical properties of an organic compound.
Q9: Name the functional group present in alcohols.
Answer: The functional group present in alcohols is the hydroxyl group (-OH).
Q10: Name the functional group present in carboxylic acids.
Answer: The functional group present in carboxylic acids is the carboxyl group (-COOH).
Q11: What is 'isomerism'?
Answer: Isomerism is the phenomenon where two or more compounds have the same molecular formula but different structural formulas and hence different chemical and physical properties.
Q12: What is the IUPAC system of nomenclature?
Answer: The IUPAC (International Union of Pure and Applied Chemistry) system of nomenclature is a systematic method for naming chemical compounds, ensuring that each compound has a unique and unambiguous name.
Q13: What happens when carbon compounds undergo 'combustion'?
Answer: When carbon compounds undergo combustion (burning in oxygen), they typically produce carbon dioxide and water, along with the release of heat and light energy.
Q14: What is the general formula for alkanes?
Answer: The general formula for alkanes is CnH2n+2, where 'n' is the number of carbon atoms.
Q15: What is the general formula for alkenes?
Answer: The general formula for alkenes is CnH2n, where 'n' is the number of carbon atoms (and n ≥ 2).
Application-Based Questions
Q16: Explain why carbon forms covalent bonds rather than ionic bonds.
Answer: Carbon forms covalent bonds because it has 4 valence electrons. To achieve a stable octet, it would either need to gain 4 electrons (forming C⁴⁻) or lose 4 electrons (forming C⁴⁺). Both processes require a very high amount of energy and are energetically unfavorable. Therefore, carbon prefers to share its valence electrons with other atoms to form strong covalent bonds, achieving stability.
Q17: Describe the 'addition reaction' of unsaturated hydrocarbons.
Answer: Addition reactions are characteristic of unsaturated hydrocarbons (alkenes and alkynes). In these reactions, atoms or groups of atoms are added across the double or triple bond, converting the unsaturated compound into a saturated one. For example, hydrogenation is an addition reaction where hydrogen gas is added across a double bond in the presence of a catalyst (like Ni or Pd) to form an alkane.
Q18: What is 'ethanol' and what are its main uses?
Answer: Ethanol (C₂H₅OH) is an alcohol. Its main uses include: 1. As an active ingredient in alcoholic beverages. 2. As a solvent in medicines (e.g., tincture of iodine), cough syrups, and many chemical reactions. 3. As a fuel (e.g., in some vehicles as gasohol) and a component in hand sanitizers.
Q19: What is 'ethanoic acid' and what is its common name?
Answer: Ethanoic acid (CH₃COOH) is a carboxylic acid. Its common name is acetic acid. It is the main component of vinegar (a 5-8% solution of acetic acid in water).
Q20: Explain the difference between 'soaps' and 'detergents'.
Answer: * Soaps: Are sodium or potassium salts of long-chain fatty acids. They work well in soft water but form scum (insoluble precipitate) with hard water. * Detergents: Are generally sodium salts of long-chain benzene sulphonic acids or long-chain alkyl hydrogen sulphates. They work effectively in both soft and hard water as they do not form insoluble precipitates with hard water ions.
Higher-Order Thinking Questions
Q21: Why are carbon compounds so numerous and diverse compared to compounds of other elements?
Answer: Carbon compounds are exceptionally numerous and diverse due to two primary properties of carbon: 1. Catenation: Carbon atoms can form strong covalent bonds with other carbon atoms, leading to the formation of long chains (straight or branched), cyclic structures, and even complex three-dimensional networks. This self-linking ability is almost unique to carbon. 2. Tetravalency: Carbon has a valency of four, meaning each carbon atom can form four covalent bonds. This allows it to bond with a wide variety of other elements (like hydrogen, oxygen, nitrogen, sulfur, halogens) and with multiple other carbon atoms, creating an immense array of stable compounds with diverse structures and properties.
Q22: Describe the process of 'esterification' and its importance.
Answer: Esterification is a chemical reaction in which an alcohol reacts with a carboxylic acid to form an ester and water, typically in the presence of an acid catalyst (like concentrated sulfuric acid). The general reaction is: R-COOH + R'-OH ↔ R-COOR' + H₂O Importance: Esters are responsible for the pleasant fruity smells and flavors in many fruits and flowers, making them important in the food, perfume, and cosmetic industries. They are also used as solvents and in the production of polymers like polyesters.
Q23: How does the presence of a functional group influence the chemical properties of a carbon compound? Provide an example.
Answer: The presence of a functional group largely determines the characteristic chemical properties and reactions of a carbon compound, regardless of the length of the carbon chain. The functional group is the site of most chemical reactions. For example: * Alcohols (containing -OH): React with sodium metal to produce hydrogen gas and undergo oxidation to form aldehydes, ketones, or carboxylic acids. * Alkanes (only C-C and C-H single bonds): Are generally unreactive and undergo substitution reactions (e.g., with halogens under UV light). The functional group dictates the compound's reactivity and the types of reactions it will undergo, making it the most important part of the molecule for chemical behavior.
Q24: Explain the concept of 'homologous series' in carbon compounds.
Answer: A homologous series is a series of organic compounds in which all members have the same general formula, similar chemical properties, and show a gradual change in physical properties (like boiling point, melting point) as the molecular mass increases. Each successive member in the series differs from the next by a -CH₂ group. Examples include the alkane series (methane, ethane, propane, butane), alcohol series (methanol, ethanol, propanol), and carboxylic acid series (methanoic acid, ethanoic acid, propanoic acid).
Q25: Why is the complete combustion of carbon compounds generally preferred over incomplete combustion?
Answer: Complete combustion of carbon compounds is generally preferred over incomplete combustion because: 1. Higher Energy Release: Complete combustion (with sufficient oxygen) produces carbon dioxide and water, releasing the maximum amount of heat energy from the fuel. Incomplete combustion (with insufficient oxygen) produces carbon monoxide (a poisonous gas) and soot (unburnt carbon particles), releasing less energy. 2. Reduced Pollution: Carbon dioxide is a greenhouse gas, but carbon monoxide is a highly toxic gas that can cause death by binding to hemoglobin in the blood. Soot is a particulate pollutant that causes respiratory problems and blackens surfaces. Complete combustion minimizes the formation of these harmful byproducts, leading to less air pollution.
Q26: Describe the process of 'saponification' and its importance in daily life.
Answer: Saponification is the chemical reaction that produces soap. It involves the hydrolysis of an ester (typically a fat or oil, which are triglycerides) with a strong base (like sodium hydroxide or potassium hydroxide) to produce glycerol and a fatty acid salt, which is soap. Importance in daily life: Saponification is fundamental to the production of all soaps used for washing, cleaning, and personal hygiene. Soaps are essential for removing dirt, grease, and microorganisms, thereby contributing to cleanliness and public health.
Q27: How can you distinguish between saturated and unsaturated hydrocarbons using a simple chemical test?
Answer: Saturated and unsaturated hydrocarbons can be distinguished using the Bromine Water Test or the Baeyer's Test (Alkaline KMnO₄ solution). * Bromine Water Test: When bromine water (reddish-brown) is added to an unsaturated hydrocarbon, the bromine adds across the double or triple bond, causing the reddish-brown color to disappear (decolorization). Saturated hydrocarbons do not react with bromine water under normal conditions, so the color persists. * Baeyer's Test: When cold, dilute, alkaline potassium permanganate solution (purple color) is added to an unsaturated hydrocarbon, the purple color disappears due to the oxidation of the unsaturated bonds. Saturated hydrocarbons do not react with Baeyer's reagent, so the purple color remains.
Q28: Discuss the concept of 'polymers' and their significance in modern society.
Answer: Polymers are large molecules (macromolecules) formed by the repetitive linking of many small, simple molecules called monomers. This process is called polymerization. Significance in modern society: Polymers are ubiquitous and indispensable in modern society. They form the basis of plastics, synthetic fibers, rubbers, and many advanced materials. They are used in: * **Packaging:** Plastic bags, bottles, containers. * **Textiles:** Nylon, polyester, rayon. * **Construction:** PVC pipes, insulation. * **Automobiles:** Tires, interior components. * **Electronics:** Insulators, circuit boards. * **Medicine:** Implants, drug delivery systems. Their versatility, durability, and low cost have revolutionized various industries and aspects of daily life.
Q29: What are 'detergents' and why are they considered superior to soaps for washing clothes in hard water?
Answer: Detergents are cleansing agents that are typically synthetic substances. Unlike soaps, they are sodium salts of long-chain benzene sulphonic acids or long-chain alkyl hydrogen sulphates. Detergents are considered superior to soaps for washing clothes in hard water because: 1. No Scum Formation: Hard water contains calcium and magnesium ions. Soaps react with these ions to form insoluble precipitates called scum, which adheres to clothes and forms a sticky residue. Detergents, however, do not form insoluble precipitates with calcium and magnesium ions. 2. Effective Lathering: Detergents produce lather readily even in hard water, allowing for effective cleaning, whereas soaps struggle to form lather in hard water due to scum formation. This makes detergents more efficient and effective cleaning agents in areas with hard water supplies.
References
- MSBSHSE Class 10 Science and Technology Textbook Part 1 (2021-22 English) - Chapter 9: Carbon Compounds
- Maharashtra State Board 10th Standard Science Syllabus 2025-26
- Balbharati Science and Technology Part 1 Textbook
- Shaalaa.com Balbharati solutions for Science and Technology 1