Practice Questions for Science Class 10th "Carbon and it's Compounds"

Multiple Choice Questions (MCQs):

1. D) 4 - Carbon has a valency of 4, forming four covalent bonds.
2. D) Nitrogen - Nitrogen is not an allotrope of carbon; diamond, graphite, and fullerene are.
3. A) Methane - Methane (CH₄) is the simplest hydrocarbon.
4. C) Ethane - Ethane (C₂H₆) is saturated with single bonds only.
5. A) Alcohols - The -OH group is characteristic of alcohols.
6. A) Hydrogenation - Vegetable oils are converted to fats by adding hydrogen, which is hydrogenation.
7. C) An ester - Ethanol (alcohol) and ethanoic acid (carboxylic acid) react to form an ester.
8. A) Vinegar - Ethanoic acid, commonly known as acetic acid, is the main component of vinegar.
9. A) Butane - CH₃-CH₂-CH₂-CH₃ is butane, a 4-carbon alkane.
10. A) Formaldehyde - Formaldehyde (HCHO) is used to preserve biological specimens.
11. A) Oxidation - Ethanol is oxidized to form ethanoic acid.
12. B) Homologous series - A series of compounds with the same functional group where each member differs by a -CH₂- unit.
13. D) Displacement - Sodium displaces hydrogen in ethanol to form sodium ethoxide.
14. A) Hydrophilic head and hydrophobic tail - Soap molecules have this structure, allowing them to interact with both water and oil.
15. C) Hydrogen sulfide - H₂S gives the characteristic smell of rotten eggs.
16. B) Aldehydes - The -CHO group is the characteristic of aldehydes.
17. A) High melting and boiling points - This is not generally true for carbon compounds, which often have low melting and boiling points due to weak van der Waals forces.
18. B) Cracking - Large hydrocarbons are broken down into smaller ones through cracking.
19. C) Alkynes - Triple bonds in hydrocarbons give them the name alkynes.
20. B) Acetone - Acetone is commonly used as a solvent in nail polish remover.

Short Answer Questions:

21. Covalent Bond: A bond formed by sharing electrons. Carbon forms covalent bonds due to its need to achieve a stable octet; this leads to the diversity of carbon compounds.
22. Homologous Series: A series of organic compounds with similar structures and chemical properties, differing by a -CH₂- group. Example: Alkanes like methane (CH₄), ethane (C₂H₆), propane (C₃H₈).
23. Saturated vs. Unsaturated Hydrocarbons: Saturated hydrocarbons (alkanes) have only single bonds, while unsaturated hydrocarbons (alkenes, alkynes) have double or triple bonds, allowing for addition reactions.
24. Carbon's Compound Formation: Carbon can form bonds with other carbon atoms (catenation) and with many other elements, leading to a vast number of compounds due to its tetravalency and ability to form stable covalent bonds.
25. Isomerism: Molecules with the same molecular formula but different structural arrangements are isomers. Example: Butane (C₄H₁₀) has two isomers - n-butane and isobutane.
26. Soap Formation (Saponification): Soap is made by hydrolyzing fats or oils with an alkali, typically sodium or potassium hydroxide, to produce glycerol and fatty acid salts (soap).
27. Diamond Structure: Carbon atoms in diamond are arranged in a tetrahedral lattice, giving it extreme hardness, high melting point, and non-conductivity due to no free electrons.
28. Ethanol Uses: As an antiseptic, solvent, fuel (bioethanol), in alcoholic beverages, and in pharmaceuticals.
29. Functional Group: An atom or group of atoms responsible for the characteristic chemical reactions of a molecule. Examples include -OH (alcohols), -COOH (carboxylic acids).
30. Distinguishing Ethanol from Ethanoic Acid: Ethanol reacts with sodium to produce hydrogen gas, while ethanoic acid does not. Also, litmus test: ethanoic acid turns blue litmus red, ethanol does not.
31. Poor Conduction: Carbon compounds are generally poor conductors because they involve covalent bonding, which does not allow for free electrons or ions to move and conduct electricity.
32. Carbon in Coal and Petroleum: Over millions of years, dead plant and animal matter rich in carbon get transformed under heat and pressure into coal and petroleum.
33. Fermentation: Yeast converts sugars into ethanol and carbon dioxide under anaerobic conditions, used in brewing and baking.
34. Carbon Cycle: Essential for life, it involves the circulation of carbon in various forms through the biosphere, ensuring the balance of CO₂ in the atmosphere, crucial for photosynthesis.
35. Graphite vs. Diamond: Graphite has a layered structure with weak forces between layers, making it soft and a good conductor due to free electrons, while diamond is a rigid 3D lattice.
36. Chemical Formulas: Methane - CH₄, Ethane - C₂H₆, Ethene - C₂H₄.
37. Weak Acid: Ethanoic acid ionizes only partially in water, hence it's a weak acid; it doesn't completely dissociate into ions.
38. Double Bond Impact: Alkenes are more reactive due to the double bond; they can undergo addition reactions where the double bond breaks to form single bonds with new atoms.
39. Addition vs. Substitution: Addition reactions involve adding atoms to a molecule, usually at a double or triple bond. Substitution reactions involve replacing one atom or group with another.
40. Soap Micelles: The hydrophobic tails of soap molecules cluster inward away from water, while hydrophilic heads face outward, trapping oil or dirt in the center for removal.

Long Answer Questions:

41. Carbon Versatility: Carbon's ability to form stable bonds with itself (catenation) and other elements, its tetravalency, and its capability to form single, double, and triple bonds allow for an immense variety of compounds.
42. Allotropes of Carbon:

• Diamond: Hard due to tetrahedral bonding, used in cutting tools.
• Graphite: Layered structure, used in pencils and as a lubricant.
• Fullerene: Cage-like structure, potential in drug delivery and nanotechnology.

43. Esterification: Reaction between an alcohol and a carboxylic acid to form an ester and water. Example: ethanol + ethanoic acid → ethyl ethanoate + water. Industrially, used in making flavors, fragrances, and plastics.
44. Environmental Impact:

• Pollution: Carbon compounds like hydrocarbons contribute to air pollution.
• Climate Change: CO₂ from burning fossil fuels enhances the greenhouse effect.
• Solutions involve reducing emissions, using renewable energy, and carbon capture technologies.

45. Alcohols, Carboxylic Acids, Esters:

• Alcohols: -OH group, polar, can form hydrogen bonds.
• Carboxylic Acids: -COOH group, acidic due to hydrogen in -COOH.
• Esters: Formed from alcohols and acids, fragrant, used in perfumes.

46. Ethanol:

• Production: From fermentation or synthetic processes.
• Properties: Colorless, volatile, flammable liquid with a characteristic smell.
• Uses: Fuel, solvent, in beverages, and in pharmaceuticals.

47. Reactions Comparison:

• Alkanes: Undergo substitution reactions, e.g., with halogens.
• Alkenes: Undergo addition reactions due to double bonds.
• Alkynes: Can undergo both addition and polymerization due to triple bonds.

48. Soaps and Detergents:

• Work by reducing surface tension, forming micelles to encapsulate dirt or oil. Detergents are synthetic, effective in hard water, while soaps can form scum with calcium or magnesium ions.

49. Hydrocarbons as Energy:

• Extraction: From fossil fuels via drilling or mining.
• Refining: Crude oil is refined into various products.
• Environmental Considerations: Pollution, finite nature of resources, push towards renewable alternatives.

50. Physical Properties:

• Melting and boiling points are influenced by molecular mass, branching, and intermolecular forces like van der Waals and hydrogen bonding.

51. Hydrogenation of Oils:

• Process adds hydrogen to unsaturated fats, increasing saturation, solidifying them. Nutritionally, it can increase trans fats, linked to health issues.

52. Carbon in Biological Systems:

• Carbon forms the backbone of macromolecules like carbohydrates (energy storage), lipids (membranes), proteins (enzymes, structure), and nucleic acids (genetic information).

53. Functional Groups:

• Alter reactivity, polarity, solubility, and biological activity. For example, -OH in alcohols makes them polar, -COOH in acids contributes to acidity.

54. Health and Safety:

• Alcohols: Can be toxic or flammable; ethanol is safer for consumption but still has health implications with overuse.
• Aldehydes: Formaldehyde is toxic and carcinogenic.
• Ketones: Acetone, while less toxic, can affect the central nervous system.

55. Polymerization:

• Joining of monomers to form polymers. Natural (e.g., cellulose) vs. synthetic (e.g., polyethylene). Mechanism can be addition or condensation polymerization.

56. Combustion of Hydrocarbons:

• Complete: Produces CO₂ and H₂O (e.g., CH₄ + 2O₂ → CO₂ + 2H₂O).
• Incomplete: Can produce CO, soot, and less water due to insufficient oxygen.

57. Greenhouse Effect:

• CO₂ from burning carbon compounds traps heat. Mitigation includes reducing emissions, afforestation, and carbon sequestration technologies.

58. Synthetic Fibers:

• Involves polymerization of monomers like ethylene to produce polymers like polyester or nylon through processes like condensation or addition reactions.

59. Waste Management:

• Challenges: Biodegradability, pollution from incineration or landfill. Solutions: Recycling, biodegradable plastics, and reducing plastic use.

60. Chirality:

• Compounds with non-superimposable mirror images (enantiomers) due to an asymmetric carbon atom. Significant in pharmaceuticals where one enantiomer might be effective, and the other harmful.

Application-Based Questions:

61. Ethanol and Sodium Reaction:

• 2C₂H₅OH + 2Na → 2C₂H₅ONa + H₂

62. Aldehyde Test:

• Tollen's reagent or Fehling's solution; a silver mirror or brick-red precipitate indicates an aldehyde.

63. Heating Ethanol with Sulfuric Acid:

• Dehydration to ethene (C₂H₄)

64. Molecular Mass of Ethanoic Acid:

• CH₃COOH: (12×2) + (1×4) + (16×2) = 24 + 4 + 32 = 60 g/mol

65. Structural Formula for Propan-2-ol:

• CH₃-CH(OH)-CH₃

66. Methane to Chloromethane:

• Methane reacts with chlorine in the presence of UV light or heat:
  • CH₄ + Cl₂ → CH₃Cl + HCl

67. Combustion of Propane:

• C₃H₈ + 5O₂ → 3CO₂ + 4H₂O (Complete combustion)

68. Differentiating Propanol from Propanone:

• Iodoform Test: Propanone (ketone) will give a yellow precipitate with iodine and NaOH, while propanol (alcohol) will not.

69. Ester Formation:

• CH₃CH₂OH + CH₃COOH → CH₃COOCH₂CH₃ + H₂O (Ethyl ethanoate formation)

70. Soap Preparation:

• Heat vegetable oil with sodium hydroxide (saponification):
  • Fat + 3NaOH → Soap (sodium salt of fatty acid) + Glycerol

Critical Thinking Questions:

71. Organic Solvents vs. Water:

• Preferred when dealing with non-polar or slightly polar substances due to better solubility, lower boiling points for reactions requiring heat, and sometimes avoiding hydrolysis.

72. Ethanol as Biofuel - Ethical Considerations:

• Benefits include lower emissions and renewable source but raises concerns about food vs. fuel debates, land use, and impact on food prices.

73. Carbon Compounds and Smog:

• Hydrocarbons contribute to photochemical smog by reacting with nitrogen oxides in sunlight, forming ozone and other harmful substances.

74. Non-Renewable Nature of Fossil Fuels:

• Formation takes millions of years; current consumption rates far exceed natural replenishment, making them non-renewable.

75. Solubility of Carbon Compounds:

• Generally non-polar or weakly polar, leading to poor solubility in water (polar) but good solubility in organic solvents (often non-polar or less polar).

76. Fullerenes in Nanotechnology:

• Their cage structure allows for drug encapsulation, potential in electronics due to conductivity, and applications in lubricants or as catalysts.

77. Sustainability of Plastics:

• Plastics offer durability and versatility but pose disposal challenges. Sustainable practices include biodegradable plastics, recycling, and reducing single-use plastics.

78. Carbon Compounds and Climate Change:

• Understanding carbon compounds helps in assessing CO₂ emissions, their role in the greenhouse effect, and strategies for carbon sequestration or reduction.

79. Impact of Carbon Nanomaterials:

• Health concerns include toxicity and bioaccumulation, while environmental impacts relate to persistence and potential disruption of ecosystems. Research into safe handling and disposal is crucial.

80. Carbon Compounds as Environmental Solutions:

• Carbon capture and storage, use of bio-based carbon compounds, carbon-negative technologies like biochar, and promoting carbon cycling through sustainable practices can mitigate environmental issues.