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Carbon and its Compounds

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NCERT Solutions for Class 10 Science Chapter 4

The chapter Carbon and its Compounds explores the unique properties of carbon and the vast variety of compounds it forms. Here are the key takeaways:

  • Carbon’s Structure: Carbon has four valence electrons, allowing it to form four covalent bonds with other atoms.
  • Catenation: A crucial property, carbon atoms can bond with each other to form long chains, rings, and branched structures, leading to a diverse range of molecules.
  • Allotropes: Carbon exists in different forms with distinct properties, like diamond (hardest natural substance) and graphite (good conductor).
  • Hydrocarbons: These organic compounds contain only carbon and hydrogen atoms. Examples include alkanes (like methane, CH₄), alkenes (double bond, like ethene, C₂H₄), and alkynes (triple bond, like ethyne, C₂H₂).
  • Functional Groups: The introduction of functional groups (like hydroxyl -OH or carbonyl C=O) into hydrocarbons creates new classes of organic compounds with specific properties. Examples include alcohols (ethanol, CH₃CH₂OH), carboxylic acids (acetic acid, CH₃COOH), and esters (sweet-smelling compounds).
  • Saturated and Unsaturated Compounds: Saturated hydrocarbons have only single bonds between carbon atoms, while unsaturated hydrocarbons contain double or triple bonds.
  • Importance of Carbon Compounds: They form the basis of life (carbohydrates, proteins, fats, nucleic acids) and have numerous applications in fuels, plastics, fibers, and medicines.

Additional points to remember:

  • Fossil fuels (coal, petroleum) are naturally occurring mixtures of hydrocarbons.
  • Combustion of hydrocarbons releases energy, making them valuable fuels.
  • However, incomplete combustion can produce harmful pollutants like carbon monoxide (CO).

NCERT Solutions for Class 10 Science Chapter 4 : Carbon and its Compounds

Questions (Page 61)

1. What would be the electron dot structure of carbon dioxide which has the formula CO2 ?

Ans : Here’s the electron dot structure of carbon dioxide (CO2):

:Ö   :Ö   :

C—O—C

:   :   :

2. What would be electron dot structure of sulphur which is made up of eight atoms of sulphur.

        S-S

        /   \

       S—S

      /     \

     S——-S

Questions (Page 68-69)

1. How many structural isomers can you draw for pentane ?

Ans : 

  • n-pentane (straight chain):
  • Image of npentane structure
  • isopentane (branched chain):
  • Image of isopentane structure
  • neopentane (branched chain):
  • Image of neopentane structure

2. What are the two properties of carbon which lead to the huge number of carbon compounds we see around us ?

Ans : The two key properties of carbon that contribute to the vast number of carbon compounds we see around us are:

  1. Catenation: This refers to the ability of carbon atoms to bond with each other by forming strong covalent bonds. Carbon atoms can link together in single, double, or even triple bonds, and these chains can be straight or branched. This ability to form various carbon-carbon skeletons allows for a massive number of different backbones for organic molecules.
  2. Tetravalency: Carbon has four valence electrons, meaning it can form four covalent bonds with other atoms. This allows carbon to bond with a wide variety of other elements, including hydrogen, oxygen, nitrogen, sulfur, halogens, and other carbons. The different combinations of these elements with carbon, along with the variations in carbon-carbon bonding, lead to an enormous range of possible molecular structures and functionalities.

3. What will be the formula and electron dot structure of cyclopentane ?

Ans :

4. Draw the structures for the following compounds :

(i) Ethanoic acid

(ii) Bromopentane

(iii) Butanone

(iv) Hexanal

Ans : 

(i)

(ii)

(iii)

(iv)

1. 1-Bromopentane (n-Pentyl bromide):

  Br

   |

 CH3-CH2-CH2-CH2-CH3

2. 2-Bromopentane (sec-Pentyl bromide):

  CH3

   |

  Br-CH2-CH2-CH2-CH3

5. How would you name the following compounds ?

NCERT Solutions for Class 10 Science Chapter 4 Carbon and its Compounds Intext Questions p68 q5

Ans : 

(i) Bromoethane

(ii) Methanal

(iii) 1 – Hexyne

NCERT Solutions for Class 10 Science Chapter 4 : Carbon and its Compounds

Questions (Page 71)

1. Why is the conversion of ethanol to ethanoic acid an oxidation reaction ?

Ans : Ethanol to ethanoic acid is an oxidation reaction for two reasons:

  1. Carbon Gets More Positive: The carbon in ethanol loses electrons (increases oxidation state) as it bonds more oxygen in the final acid.
  2. Loses Hydrogen: Oxidation can also involve losing hydrogen (along with its electron). Ethanol loses a hydrogen during the conversion.

2. A mixture of oxygen and ethyne is burnt for welding. Can you tell why a mixture of ethyne and air is not used ?

Ans : A mixture of ethyne (also called acetylene) and air is not used for welding because it wouldn’t provide the necessary conditions for an effective weld. Here’s why:

  • Incomplete Combustion: Air is only about 21% oxygen, while the rest is mainly nitrogen. This limited oxygen supply wouldn’t allow for complete combustion of ethyne.
  • Lower Temperature: Incomplete combustion generates less heat compared to complete combustion. Welding requires a very high temperature to melt the metals and create a strong bond.
  • Sooty Flame: Incomplete combustion often produces soot (unburned carbon particles) which can contaminate the weld and make it weaker.

Questions (Page 74)

1. How would you distinguish experimentally between an alcohol and a carboxylic acid ?

Ans : 

TestObservation (Alcohol)Observation (Carboxylic Acid)
Sodium Bicarbonate (NaHCO₃) TestNo reaction, no gas evolutionBrisk effervescence (fizzing) with colorless, odorless gas evolution (CO₂)
Litmus Test (Moist Litmus Paper)No change in colorLitmus paper turns red

2. What are oxidising agents ?

Ans : Oxidizing agents (oxidants) are electron thieves! They steal electrons from other substances (reducing agents) during reactions. This makes them gain electrons (get reduced) while the other substance loses electrons (gets oxidized). Common examples include oxygen gas, halogens (chlorine), and hydrogen peroxide.

NCERT Solutions for Class 10 Science Chapter 4 : Carbon and its Compounds

Questions (Page 76)

1. Would you be able to check if water is hard by using a detergent ?

Ans : Nope! Detergent lathers in both hard and soft water, so it’s not a reliable test. Soap forms scum in hard water, but detergent doesn’t. Try a soap test or hardness test strips for a better answer.

2. People use a variety of methods to wash clothes. Usually after adding the soap, they ‘beat’ the clothes on a stone, or beat it with a paddle, scrub with a brush or the mixture is agitated in a washing machine. Why is agitation necessary to get clean clothes ?

Ans : Agitation is necessary to get clean clothes for two main reasons:

  1. Dislodging Dirt:  Soap molecules surround and loosen dirt particles from the fabric. Agitation, whether by hand or machine, helps to physically dislodge these loosened dirt particles from the fibers and suspend them in the wash water. Without agitation, the loosened dirt might simply stick back onto the clothes.
  2. Improving Soap Effectiveness:  Agitation helps to distribute the soapy water throughout the fabric, ensuring better contact between the soap molecules and dirt particles. This allows the soap to work more effectively in trapping and removing dirt.

So, agitation acts like a helping hand for the soap, making the cleaning process more efficient by removing loosened dirt and maximizing the soap’s reach.

NCERT Solutions for Class 10 Science Chapter 4 : Carbon and its Compounds

Exercises

1. Ethane, with the molecular formula C2H6 has

(a) 6 covalent bonds

(b) 7 covalent bonds

(c) 8 covalent bonds

(d) 9 covalent bonds

Ans : (b) 7 covalent bonds

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

(a) carboxylic acid

(b) aldehyde

(c) ketone

(d) alcohol

Ans : (c) ketone

3. 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.

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

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

Ans : In CH3Cl, carbon and chlorine share electrons to form a covalent bond. However, chlorine is more greedy for electrons (electronegative). This unequal sharing creates a polar covalent bond, with a slight negative end on chlorine (δ-) and a slight positive end on carbon (δ+). The shared electrons spend more time near chlorine than carbon.

5. Draw the electron dot structures for

(a) ethanoic acid

(b) propanone

(c) H2S

(d) F2.

Ans : 

6. What is a homologous series ? Explain with an example.

Ans :A homologous series is a group of organic compounds that share similar structures and properties. Here’s a breakdown:

Key Features:

  • Same Functional Group: All members of a homologous series contain the same functional group, which is an atom or group of atoms responsible for the characteristic chemical behavior of the molecule.
  • Carbon Chain Variation: They differ from each other by a constant unit, typically a CH₂ (methylene) group, in their carbon chain length.
  • Gradual Property Change: As the chain length increases, the physical properties of the compounds within the series gradually change.

Example: Alkanes

Let’s consider alkanes, a common homologous series. They are hydrocarbons (compounds containing only carbon and hydrogen) with single bonds between all their atoms.

  • Functional Group: All alkanes share the same functional group, which is simply carbon-hydrogen single bonds (C-H).
  • Carbon Chain Variation: Methane (CH₄) has one carbon atom, ethane (C₂H₆) has two, propane (C₃H₈) has three, and so on. Each subsequent alkane has one more CH₂ unit compared to the previous one.
  • Property Change: As the chain length increases, the boiling point, melting point, and viscosity of the alkanes generally increase. This is because there are more intermolecular forces (forces of attraction between molecules) with longer chains.

Benefits of Studying Homologous Series:

  • Understanding homologous series helps predict the properties of a compound based on its position in the series and the properties of its neighbors.
  • It simplifies the study of organic chemistry as many properties and reactions follow predictable trends within a series.

In essence, homologous series provide a systematic way to organize organic compounds based on their structure and properties, making it easier to understand and predict their behavior.

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

Ans : 

Physical Properties : 

PropertyEthanolEthanoic Acid
AppearanceColorless liquidColorless liquid with pungent odor
Boiling PointLower (around 78°C)Higher (around 118°C)
Solubility in WaterMore solubleSoluble

Chemical Properties : 

PropertyEthanolEthanoic Acid
Sodium Bicarbonate TestNo reactionFizzing due to CO₂ gas evolution
Litmus TestNo changeSlight reddening (dry), red (moist)

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

Ans : Soap has a double personality: a water-loving head and an oil-loving tail. In water, the tails clump together to avoid water, while the heads stay happy at the water’s edge. This cluster is called a micelle.

Micelles are less likely in ethanol (alcohol) because ethanol isn’t as good with water (less polar) and can also bond with the soap heads, reducing the need for them to huddle together. So, soap makes micelles in water to avoid getting lonely, but not so much in ethanol.

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

Ans : 

  1. Energy Packed Bonds: Carbon bonds store a lot of energy, releasing heat when broken during burning.
  2. Fuel Variety: From gas to liquid to solid (think methane, gasoline, coal), carbon offers options.
  3. Easy to Find: We have plenty of carbon on Earth as fossil fuels and in plants.
  4. Ready to Burn: Many carbon fuels ignite easily at reasonable temperatures.
  5. Controllable Burn: We can adjust how fast these fuels burn for efficient energy use.

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

Ans : Scum formation in hard water with soap is a battle between attraction and repulsion:

  • Hard Water Culprits: Hard water contains dissolved calcium (Ca²⁺) and magnesium (Mg²⁺) ions.
  • Soap Attraction: Soap molecules (like sodium stearate) have a long, greasy tail and a charged head that loves water. This head attracts the positively charged Ca²⁺ and Mg²⁺ ions in hard water.

The Problem:

  • Sticky Situation: Instead of forming soapy suds for cleaning, the soap molecules get tangled up with the calcium and magnesium ions.
  • Scum is Born: These tangled clusters are insoluble in water and form a greasy, white layer floating on the water or clinging to surfaces – scum.

The Result:

  • Less Cleaning Power: Scum formation reduces the effectiveness of soap in removing dirt and grease because there are fewer free soap molecules available for cleaning.

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

Ans : Testing soap with litmus paper reveals its basic nature:

  • Blue litmus paper: Turns red. Soap is slightly basic, and bases turn blue litmus red.
  • Red litmus paper: No change. Red litmus paper indicates acids, and soap isn’t acidic enough to cause a change.

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

Ans : Hydrogenation: Adding Hydrogen for Diverse Applications

Hydrogenation is a chemical reaction where hydrogen (H₂) is added to another compound, usually in the presence of a catalyst (like nickel, palladium, or platinum). This process plays a crucial role in various industrial applications.

The Key Reaction:

  • Unsaturated compounds, containing double or triple bonds between carbon atoms, react with hydrogen to become saturated. Saturated compounds have only single bonds between carbon atoms.

Industrial Applications:

  • Food Industry:
    • Hydrogenation is used to convert unsaturated vegetable oils (liquid) into saturated fats (more solid) for products like margarine, shortening, and cooking fats. This increases shelf life and stability.
  • Petrochemical Industry:
    • Hydrogenation helps refine crude oil fractions by converting unsaturated hydrocarbons into more desirable products like gasoline and diesel.
  • Other Applications:
    • Hydrogenation is also used in the production of various chemicals like alcohols (e.g., ethanol) and fatty acids.

13. Which of the following hydrocarbons undergo addition reactions :

C2H6, C3H8, C3H6, C2H2 and CH4

Ans : Only C3H6 (propylene) and C2H2 (acetylene) will undergo addition reactions among the given hydrocarbon options (C2H6, C3H8, C3H6, C2H2, and CH4).

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

Ans : Test: Bromine Water Test

Procedure:

  1. Take two separate test tubes.
  2. Add a small amount of the unknown substance (butter or cooking oil) to each test tube.
  3. Add a few drops of bromine water (a solution of bromine in water) to each test tube.

Observation:

  • Butter (Saturated Fat): No color change will be observed in the bromine water. Saturated fats, like those predominantly found in butter, do not react with bromine water.
  • Cooking Oil (Unsaturated Fat): The bromine water will turn colorless or become lighter in color. Unsaturated fats, common in most cooking oils, react with bromine water, causing the orange color to fade.

Explanation:

  • Bromine water is a source of Br₂, which can readily react with double bonds present in unsaturated fatty acids found in most cooking oils. This is an addition reaction where the Br₂ molecule adds across the double bond, causing the orange color to disappear.
  • Saturated fats in butter lack these double bonds, and therefore, no reaction occurs with bromine water, leaving the solution’s color unchanged.

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

Ans : Soap’s cleaning action involves a clever battle between its molecules and dirt particles, aided by water:

  1. Soap Molecule Structure: Soap molecules are amphiphilic, meaning they have a “double personality”:
    • Hydrophilic Head (Water-loving): This end, often containing a carboxylate group (COO⁻), is attracted to water because it can form hydrogen bonds with water molecules.
    • Hydrophobic Tail (Oil-loving): This end, a long hydrocarbon chain, is repelled by water and has an affinity for oils and grease.
  2. Dirt and Water Challenge: Dirt and grease are often oily or greasy substances that don’t mix well with water. This makes it difficult to remove them with water alone.
  3. Micelle Formation: When soap is added to water, its molecules arrange themselves in clusters called micelles. These micelles have the hydrophobic tails pointing inwards, away from the water, and the hydrophilic heads facing outwards, interacting with water molecules.
  4. Dirt Trapping: The hydrophobic tails of the soap molecules in the micelle act like tiny magnets for dirt and grease. These oily substances get attracted to the micelle’s interior, away from the water.
  5. Suspension and Rinse Away: With dirt and grease trapped within the micelles, they become suspended in the water and are no longer stuck to the surface being cleaned. This allows you to easily rinse them away with water.

NCERT Solutions for Class 10 Science Chapter 4 : Carbon and its Compounds

FAQs

What topics are covered in NCERT Solutions for Class 10 Science Chapter 4?

NCERT Solutions for Class 10 Science Chapter 4 cover the properties, structures, and reactions of carbon compounds. Topics include covalent bonding, versatile nature of carbon, homologous series, and important organic compounds like hydrocarbons, alcohols, carboxylic acids, and soaps and detergents.

How is the versatile nature of carbon explained in Class 10 Science Chapter 4?

Class 10 Science Chapter 4 explains that carbon’s versatile nature is due to its ability to form four covalent bonds, leading to a wide variety of compounds. This includes chains, branches, and rings, allowing for a vast number of molecular structures.

What is the significance of the homologous series as per NCERT Solutions for Class 10 Science Chapter 4?

The homologous series, as per NCERT Solutions for Class 10 Science Chapter 4, is a group of organic compounds with similar chemical properties and a gradation in physical properties. Each successive member differs by a -CH2- unit. Examples include alkanes, alkenes, and alkynes.

What are the important organic compounds discussed in Class 10 Science Chapter 4?

Important organic compounds discussed in Class 10 Science Chapter 4 include hydrocarbons (alkanes, alkenes, alkynes), alcohols, aldehydes, ketones, carboxylic acids, and esters. The chapter also covers functional groups and their properties.

How is soap and detergent action explained in NCERT Solutions for Class 10 Science Chapter 4?

NCERT Solutions for Class 10 Science Chapter 4 explain that soaps and detergents clean by emulsifying oils and dirt. Soaps form micelles that trap dirt and oil, which are then washed away with water. Detergents work similarly but are more effective in hard water.

What are covalent bonds, as described in Class 10 Science Chapter 4?

Class 10 Science Chapter 4 describes covalent bonds as bonds formed by the sharing of electrons between atoms. Carbon forms covalent bonds with other carbon atoms and elements like hydrogen, oxygen, nitrogen, and halogens, resulting in diverse organic compounds.

How are hydrocarbons classified in NCERT Solutions for Class 10 Science Chapter 4?

In NCERT Solutions for Class 10 Science Chapter 4, hydrocarbons are classified into alkanes (single bonds), alkenes (one or more double bonds), and alkynes (one or more triple bonds). Each class has distinct properties and reactivity.

What is the role of functional groups in organic chemistry as per Class 10 Science Chapter 4?

Functional groups, as per Class 10 Science Chapter 4, determine the chemical properties and reactions of organic molecules. Examples include hydroxyl (-OH), carboxyl (-COOH), and aldehyde (-CHO) groups. They are critical in the classification and reactivity of organic compounds.

How is the nomenclature of carbon compounds explained in NCERT Solutions for Class 10 Science Chapter 4?

NCERT Solutions for Class 10 Science Chapter 4 explain the nomenclature of carbon compounds using IUPAC (International Union of Pure and Applied Chemistry) rules.

Where can I find detailed NCERT Solutions for Class 10 Science Chapter 4?

Detailed NCERT Solutions for Class 10 Science Chapter 4 can be found in the NCERT textbook for Class 10 Science or on various educational websites and platforms that provide free access to these solutions.

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