Gyanyaan हिंदी

Chapter 4: Carbon and its Compounds

Class 10 Science · MCQs with answers

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  1. What type of bond does carbon form in most of its compounds?

    1. (A) Ionic bond
    2. (B) Metallic bond
    3. (C) Covalent bond
    4. (D) Hydrogen bond
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    Correct answer: (C) Covalent bond

    Explanation: Carbon cannot easily lose or gain 4 electrons. So it shares electrons with other atoms, forming covalent bonds.

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  2. What is the valency of carbon?

    1. (A) 1
    2. (B) 2
    3. (C) 3
    4. (D) 4
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    Correct answer: (D) 4

    Explanation: Carbon has 4 electrons in its outer shell, so it forms four bonds. This is called tetravalency.

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  3. What is carbon's property of bonding with other carbon atoms to form long chains called?

    1. (A) Isomerism
    2. (B) Neutralisation
    3. (C) Corrosion
    4. (D) Catenation
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    Correct answer: (D) Catenation

    Explanation: Carbon atoms joining with each other to form long chains, branches and rings is called catenation. This is why carbon has so many compounds.

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  4. What is the molecular formula of buckminsterfullerene?

    1. (A) C₆
    2. (B) C₂₀
    3. (C) C₆₀
    4. (D) C₁₀₀
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    Correct answer: (C) C₆₀

    Explanation: Buckminsterfullerene (C₆₀) is an allotrope of carbon in which 60 carbon atoms are joined in a football-like shape. Diamond and graphite are other allotropes of carbon.

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  5. Which of the following is a saturated hydrocarbon?

    1. (A) C₂H₆
    2. (B) C₂H₄
    3. (C) C₂H₂
    4. (D) C₆H₆
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    Correct answer: (A) C₂H₆

    Explanation: A saturated hydrocarbon (alkane) has only single bonds between carbon atoms, with the formula CₙH₂ₙ₊₂. Ethane (C₂H₆) is saturated; C₂H₄, C₂H₂ and C₆H₆ are unsaturated.

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  6. How many covalent bonds are there in one molecule of ethane (C₂H₆)?

    1. (A) 5
    2. (B) 6
    3. (C) 7
    4. (D) 8
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    Correct answer: (C) 7

    Explanation: Ethane has 1 bond between the two carbon atoms and 6 carbon–hydrogen bonds, making 7 bonds in total.

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  7. Which of these molecules has a triple bond?

    1. (A) O₂
    2. (B) N₂
    3. (C) CH₄
    4. (D) CO₂
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    Correct answer: (B) N₂

    Explanation: The two nitrogen atoms share three pairs of electrons, forming a triple bond (N≡N). O₂ has a double bond, CO₂ has two double bonds, and CH₄ has only single bonds.

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  8. Two successive members of a homologous series differ by which group?

    1. (A) –CH₂–
    2. (B) –CH₃
    3. (C) –OH
    4. (D) –COOH
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    Correct answer: (A) –CH₂–

    Explanation: Successive members of a homologous series differ by a –CH₂– unit, which is a difference of 14 u in molecular mass.

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  9. How many structural isomers does butane (C₄H₁₀) have?

    1. (A) 4
    2. (B) 3
    3. (C) 2
    4. (D) 1
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    Correct answer: (C) 2

    Explanation: Butane has two structural isomers: straight-chain n-butane and branched-chain isobutane. Both have the formula C₄H₁₀ but different structures.

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  10. Which functional group is present in an alcohol?

    1. (A) –CHO
    2. (B) –OH
    3. (C) –COOH
    4. (D) –Cl
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    Correct answer: (B) –OH

    Explanation: The functional group of an alcohol is –OH, as in ethanol, CH₃CH₂OH. –CHO belongs to aldehydes and –COOH to carboxylic acids.

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  11. What is the functional group of a carboxylic acid?

    1. (A) –OH
    2. (B) –CHO
    3. (C) >C=O
    4. (D) –COOH
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    Correct answer: (D) –COOH

    Explanation: Carboxylic acids have the –COOH group, as in ethanoic acid, CH₃COOH.

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  12. What is the IUPAC name of CH₃COOH?

    1. (A) Methanoic acid
    2. (B) Ethanol
    3. (C) Ethanoic acid
    4. (D) Propanoic acid
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    Correct answer: (C) Ethanoic acid

    Explanation: It has 2 carbon atoms (eth-) and the –COOH group (-oic acid), so it is ethanoic acid. It is commonly called acetic acid.

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  13. What is the IUPAC name of CH₃COCH₃?

    1. (A) Propanone
    2. (B) Propanal
    3. (C) Propanol
    4. (D) Ethanone
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    Correct answer: (A) Propanone

    Explanation: It has 3 carbon atoms (prop-) and a ketone group, >C=O, on the middle carbon (-one), so it is propanone.

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  14. What kind of flame do unsaturated hydrocarbons usually give when they burn?

    1. (A) A clean blue flame
    2. (B) A green flame
    3. (C) No flame
    4. (D) A sooty yellow flame
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    Correct answer: (D) A sooty yellow flame

    Explanation: Unsaturated hydrocarbons do not burn completely, so they give a yellow flame with black smoke (soot). Saturated hydrocarbons usually give a clean blue flame.

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  15. What does ethanol change into when heated with alkaline KMnO₄?

    1. (A) Ethane
    2. (B) Ethanoic acid
    3. (C) Ethene
    4. (D) Methanol
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    Correct answer: (B) Ethanoic acid

    Explanation: Alkaline KMnO₄ (or acidified K₂Cr₂O₇) is an oxidising agent that oxidises ethanol to ethanoic acid.

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  16. Which catalyst is used in the hydrogenation of vegetable oils?

    1. (A) Nickel
    2. (B) Copper
    3. (C) Iron
    4. (D) Sodium
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    Correct answer: (A) Nickel

    Explanation: In the presence of a nickel (or palladium) catalyst, hydrogen adds to unsaturated oils. This is an addition reaction and is used to make vanaspati ghee.

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  17. What type of reaction is CH₄ + Cl₂ → CH₃Cl + HCl, which happens in sunlight?

    1. (A) Addition reaction
    2. (B) Combustion reaction
    3. (C) Substitution reaction
    4. (D) Neutralisation
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    Correct answer: (C) Substitution reaction

    Explanation: One hydrogen atom of methane is replaced by a chlorine atom. One atom taking another's place is a substitution reaction.

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  18. Which gas is released when sodium metal reacts with ethanol?

    1. (A) Oxygen
    2. (B) Hydrogen
    3. (C) Carbon dioxide
    4. (D) Chlorine
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    Correct answer: (B) Hydrogen

    Explanation: 2Na + 2CH₃CH₂OH → 2CH₃CH₂ONa + H₂. Sodium ethoxide forms and hydrogen gas is released.

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  19. What forms when ethanol is heated at 443 K with excess concentrated sulphuric acid?

    1. (A) Ethane
    2. (B) Ethyne
    3. (C) Ethanoic acid
    4. (D) Ethene
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    Correct answer: (D) Ethene

    Explanation: Concentrated H₂SO₄ removes water from ethanol (dehydration): CH₃CH₂OH → CH₂=CH₂ + H₂O. This gives ethene.

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  20. Vinegar is a dilute solution of what?

    1. (A) Ethanol
    2. (B) Methanol
    3. (C) Ethanoic acid
    4. (D) Sulphuric acid
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    Correct answer: (C) Ethanoic acid

    Explanation: Vinegar is a 5–8% solution of ethanoic (acetic) acid in water. It is used as a preservative in pickles.

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  21. Which sweet-smelling substance forms when ethanoic acid reacts with ethanol in the presence of an acid catalyst?

    1. (A) An ester
    2. (B) Soap
    3. (C) An aldehyde
    4. (D) Ethene
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    Correct answer: (A) An ester

    Explanation: A carboxylic acid and an alcohol react to form an ester (esterification). Here ethyl ethanoate forms; it smells sweet and is used in perfumes.

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  22. What is the reaction of heating an ester with sodium hydroxide to make soap called?

    1. (A) Esterification
    2. (B) Hydrogenation
    3. (C) Dehydration
    4. (D) Saponification
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    Correct answer: (D) Saponification

    Explanation: Ester + NaOH → alcohol + sodium salt of the carboxylic acid. Sodium salts of long-chain acids are soaps, so this is called saponification.

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  23. Why doesn't soap lather well in hard water?

    1. (A) Hard water has no salt
    2. (B) Soap forms an insoluble scum with calcium and magnesium salts
    3. (C) Hard water is too hot
    4. (D) Hard water is acidic
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    Correct answer: (B) Soap forms an insoluble scum with calcium and magnesium salts

    Explanation: Hard water contains calcium and magnesium salts. Soap reacts with them to form an insoluble scum, so it does not lather.

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  24. Assertion (A): Detergents can be used even in hard water. Reason (R): Detergents do not form insoluble precipitates with calcium and magnesium ions.

    1. (A) Both A and R are true, and R is the correct explanation of A.
    2. (B) Both A and R are true, but R is not the correct explanation of A.
    3. (C) A is true, but R is false.
    4. (D) A is false, but R is true.
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    Correct answer: (A) Both A and R are true, and R is the correct explanation of A.

    Explanation: Detergents do not form scum with the ions in hard water, so they lather and clean even in hard water. R correctly explains A.

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  25. Assertion (A): Diamond is extremely hard. Reason (R): In diamond, each carbon atom is bonded to four other carbon atoms, forming a rigid three-dimensional structure.

    1. (A) Both A and R are true, and R is the correct explanation of A.
    2. (B) Both A and R are true, but R is not the correct explanation of A.
    3. (C) A is true, but R is false.
    4. (D) A is false, but R is true.
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    Correct answer: (A) Both A and R are true, and R is the correct explanation of A.

    Explanation: Diamond's hardness comes from its rigid three-dimensional structure, so R correctly explains A. (In graphite each carbon is bonded to three others, and the layers can slide.)

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