Class 10 Science · Chapter 4

Carbon and its Compounds

201 Class 10 Science questions on Carbon and its Compounds from the NCERT textbook, NCERT Exemplar and CBSE board papers 2024–2026, each with its answer and a step-by-step solution.

CBSE Class 10 Science previous year papers, with answers →

Questions · page 5 of 11

1. Q81 Exemplar · Long Answer Questions
   Look at Figure 4.1 and answer the following questions

   1. (a)What change would you ​observe in the calcium ​hydroxide solution taken ​in tube B?
   2. (b)Write the reaction involved in test tubes ​A and B respectively.
   3. (c)If ethanol ​is given instead of ethanoic acid, ​would you expect the same change?
   4. (d)How can a solution of lime water be prepared ​in the laboratory?

   Show answer

   Lime water in tube B turns milky; ethanol would not show this change; lime water is made from quick lime and water.

   (a) The clear calcium hydroxide solution in tube B turns milky, because insoluble calcium carbonate is precipitated; on passing the gas for a long time the milkiness disappears again as soluble calcium hydrogencarbonate is formed. (b) In tube A: $2{\text{CH}}_3\text{COOH}+{\text{Na}}_2{\text{CO}}_3⟶2{\text{CH}}_3\text{COONa}+{\text{H}}_2\text{O}+{\text{CO}}_2$; in tube B: ${\text{Ca(OH)}}_2+{\text{CO}}_2⟶{\text{CaCO}}_3\downarrow +{\text{H}}_2\text{O}$. (c) No. Ethanol is neutral and is a far weaker acid than carbonic acid, so it does not react with sodium carbonate; no carbon dioxide is evolved and the lime water in tube B remains clear. This is the very test by which a carboxylic acid is distinguished from an alcohol. (d) Take a small quantity of quick lime, $\text{CaO}$, in a beaker and add water; it reacts with hissing and much heat to give slaked lime, $\text{CaO}+{\text{H}}_2\text{O}\to {\text{Ca(OH)}}_2$. Stir, let the undissolved solid settle, then filter or decant off the clear liquid above; that clear saturated solution is lime water. Slaked lime shaken with water and allowed to settle serves equally well.

   Step-by-step solution →
2. Q82 Exemplar · Long Answer Questions
   How would you bring about the following conversions? Name ​the process ​and write the reaction involved. ​

   1. (a)ethanol to ethene.
   2. (b)propanol to propanoic acid. Write ​the reactions.
   Show answer

   Ethanol to ethene by dehydration with hot concentrated sulphuric acid; propanol to propanoic acid by oxidation with alkaline potassium permanganate.

   (a) Ethanol to ethene: the process is dehydration. Ethanol is heated at 443 K with excess concentrated sulphuric acid, which removes a molecule of water from it. ${\text{CH}}_3{\text{CH}}_2\text{OH}\underset{443\text{K}}{\overset{{\text{conc. H}}_2{\text{SO}}_4}{\to }}{\text{CH}}_2={\text{CH}}_2+{\text{H}}_2\text{O}$. (b) Propanol to propanoic acid: the process is oxidation. Propanol is warmed with alkaline potassium permanganate, or with acidified potassium dichromate, which supplies the oxygen that converts the $-{\text{CH}}_2\text{OH}$ group into a $-\text{COOH}$ group. ${\text{CH}}_3{\text{CH}}_2{\text{CH}}_2\text{OH}\underset{\text{heat}}{\overset{{\text{alk. KMnO}}_4}{\to }}{\text{CH}}_3{\text{CH}}_2\text{COOH}$.

   Step-by-step solution →
3. Q83 Exemplar · Long Answer Questions
   Draw the ​possible ​isomers ​of ​the ​compound with molecular formula ${\text{C}}_3{\text{H}}_6\text{O}$ and also ​give their electron ​dot structures.
   Show answer

   Two isomers: propanal ${\text{CH}}_3{\text{CH}}_2\text{CHO}$ and propanone ${\text{CH}}_3{\text{COCH}}_3$, each with 24 valence electrons (12 pairs) in the dot structure.

   ${\text{C}}_3{\text{H}}_6\text{O}$ is two hydrogen atoms short of the saturated ${\text{C}}_3{\text{H}}_8\text{O}$, so it contains one double bond, and with an oxygen present that is a carbonyl group. On a three-carbon chain the carbonyl group can sit at an end or in the middle, which gives the two isomers. (i) Propanal, ${\text{CH}}_3-{\text{CH}}_2-\text{CHO}$, an aldehyde, in which the carbonyl carbon carries one hydrogen. (ii) Propanone, ${\text{CH}}_3-\text{CO}-{\text{CH}}_3$, a ketone, in which the carbonyl carbon carries two methyl groups. Each molecule has $3\times 4+6\times 1+6=24$ valence electrons, that is 12 pairs. In both electron dot structures these appear as 6 shared pairs between carbon and hydrogen, 2 shared pairs between the carbon atoms, 2 shared pairs in the carbon-oxygen double bond and 2 lone pairs on the oxygen, so every carbon has an octet, the oxygen has an octet and every hydrogen a duplet.

   Step-by-step solution →
4. Q84 Exemplar · Long Answer Questions
   Explain the ​given reactions ​with the ​examples ​

   1. (a)​Hydrogenation reaction
   2. (b)Oxidation reaction
   3. (c)Substitution reaction
   4. (d)Saponification ​reaction
   5. (e)Combustion reaction
   Show answer

   Hydrogenation adds hydrogen; oxidation adds oxygen; substitution replaces an atom; saponification is alkaline hydrolysis of an ester; combustion is burning in oxygen.

   (a) Hydrogenation is the addition of hydrogen to an unsaturated compound in the presence of a catalyst such as nickel; the multiple bond becomes a single bond and nothing leaves the molecule. Example: ${\text{CH}}_2={\text{CH}}_2+{\text{H}}_2\stackrel{\text{Ni}}{\to }{\text{CH}}_3-{\text{CH}}_3$; it is used to harden vegetable oils into vanaspati. (b) Oxidation is the gain of oxygen or the loss of hydrogen, brought about by an oxidising agent; alcohols are oxidised to carboxylic acids. Example: ${\text{CH}}_3{\text{CH}}_2\text{OH}\underset{\text{heat}}{\overset{{\text{alk. KMnO}}_4}{\to }}{\text{CH}}_3\text{COOH}$. (c) In a substitution reaction one atom or group of a saturated compound is replaced by another, the displaced atom leaving with the reagent. Example: ${\text{CH}}_4+{\text{Cl}}_2\stackrel{\text{sunlight}}{\to }{\text{CH}}_3\text{Cl}+\text{HCl}$. (d) Saponification is the hydrolysis of an ester by an alkali, giving the salt of the carboxylic acid and the alcohol. Example: ${\text{CH}}_3{\text{COOC}}_2{\text{H}}_5+\text{NaOH}\to {\text{CH}}_3\text{COONa}+{\text{C}}_2{\text{H}}_5\text{OH}$; with a fat or oil it gives soap and glycerol, which is how the process is named. (e) Combustion is the burning of a substance in oxygen with the evolution of heat and light, carbon compounds giving carbon dioxide and water. Example: ${\text{CH}}_4+2{\text{O}}_2\to {\text{CO}}_2+2{\text{H}}_2\text{O}+$ heat and light.

   Step-by-step solution →
5. Q85 Exemplar · Long Answer Questions
   An ​organic compound A on heating with concentrated ${\text{H}}_2{\text{SO}}_4$ forms a compound B which on addition of one mole ​of hydrogen in ​presence ​of ​Ni forms a compound C. One mole of compound C on combustion forms two moles of ${\text{CO}}_2$ ​and 3 moles of ${\text{H}}_2\text{O}$. Identify the compounds A, ​B and C and write the chemical equations of the reactions involved.
   Show answer

   A is ethanol, B is ethene and C is ethane, found from the combustion data and the reactions.

   A is ethanol, ${\text{C}}_2{\text{H}}_5\text{OH}$; B is ethene, ${\text{C}}_2{\text{H}}_4$; and C is ethane, ${\text{C}}_2{\text{H}}_6$. One mole of C gives 2 mol of carbon dioxide and 3 mol of water, so one molecule of C has 2 carbon atoms and $2\times 3=6$ hydrogen atoms, that is ethane; B is C less one molecule of hydrogen, that is ethene; and the compound that gives ethene on being heated with concentrated sulphuric acid is ethanol. The reactions are ${\text{C}}_2{\text{H}}_5\text{OH}\underset{443\text{K}}{\overset{{\text{conc. H}}_2{\text{SO}}_4}{\to }}{\text{C}}_2{\text{H}}_4+{\text{H}}_2\text{O}$, then ${\text{C}}_2{\text{H}}_4+{\text{H}}_2\stackrel{\text{Ni}}{\to }{\text{C}}_2{\text{H}}_6$, and finally $2{\text{C}}_2{\text{H}}_6+7{\text{O}}_2⟶4{\text{CO}}_2+6{\text{H}}_2\text{O}$.

   Step-by-step solution →
6. Q86 CBSE 2026
   How many bonds ​can ​one ​carbon ​atom ​form in ​a ​compound ?

   1. (a)$1$
   2. (b)$2$
   3. (c)$4$
   4. (d)$6$
   Show answer

   (c) $4$

   Step-by-step solution →
7. Q87 CBSE 2026
   The ​number ​of ​isomers ​of butane ​is

   1. (a)$1$
   2. (b)$2$
   3. (c)$3$
   4. (d)$4$
   Show answer

   (b) $2$

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8. Q88 CBSE 2026
   Which ​of ​the ​following ​is ​the name ​of compound $\text{H}-\stackrel{\stackrel{\text{H}}{|}}{C}=\text{O}$ ?

   1. (a)Methane
   2. (b)Methanal
   3. (c)Methanol
   4. (d)Methanoic acid
   Show answer

   (b) Methanal

   Step-by-step solution →
9. Q89 CBSE 2026
   Which ​of the ​following ​set of compounds does ​not ​belong to ​same homologous series ?

   1. (a)${\text{CH}}_4$ and ${\text{C}}_4{\text{H}}_{10}$
   2. (b)${\text{C}}_2{\text{H}}_6$ and ${\text{C}}_3{\text{H}}_8$
   3. (c)${\text{C}}_3{\text{H}}_8$ and ${\text{C}}_5{\text{H}}_{12}$
   4. (d)${\text{C}}_4{\text{H}}_8$ and ${\text{C}}_5{\text{H}}_{12}$
   Show answer

   (d) ${\text{C}}_4{\text{H}}_8$ and ${\text{C}}_5{\text{H}}_{12}$

   Step-by-step solution →
10. Q90 CBSE 2026
    Butanal ​is a ​four-carbon ​compound ​with ​the ​functional group ​:

    1. (a)Carboxylic acid
    2. (b)Aldehyde
    3. (c)Ketone
    4. (d)Alcohol
    Show answer

    (b) Aldehyde

    Step-by-step solution →
11. Q91 CBSE 2026
    Butanone ​is ​a four-carbon ​compound ​with ​the functional ​group ​:

    1. (a)Carboxylic acid
    2. (b)Aldehyde
    3. (c)Ketone
    4. (d)Alcohol
    Show answer

    (c) Ketone

    Step-by-step solution →
12. Q92 CBSE 2026
    Butanoic ​acid is ​a ​four-carbon ​compound ​with the ​functional group ​:

    1. (a)Carboxylic acid
    2. (b)Aldehyde
    3. (c)Ketone
    4. (d)Alcohol
    Show answer

    (a) Carboxylic acid

    Step-by-step solution →
13. Q93 CBSE 2026
    Identify ​the ​unsaturated ​compounds from ​the ​following :

    1. (i)Propane
    2. (ii)​Propene
    3. (iii)​Propyne
    4. (iv)Chloropropane

    1. (a)(i) and (ii)
    2. (b)(ii) and (iv)
    3. (c)(iii) and (iv)
    4. (d)(ii) and (iii)
    Show answer

    (d) (ii) and (iii)

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14. Q94 CBSE 2026
    Which ​of ​the following ​compounds will ​undergo ​addition ​reaction ?

    1. (a)${\text{C}}_3{\text{H}}_8$
    2. (b)${\text{C}}_4{\text{H}}_8$
    3. (c)${\text{C}}_2{\text{H}}_6$
    4. (d)${\text{C}}_4{\text{H}}_{10}$
    Show answer

    (b) ${\text{C}}_4{\text{H}}_8$

    Step-by-step solution →
15. Q95 CBSE 2026
    While ​washing ​dirty clothes by ​soap, micelles are ​formed. ​Select ​the correct statement about ​micelles.

    1. (a)The hydrophobic tail of the soap molecule is in the interior of the cluster, whereas hydrophilic end is on the surface of the cluster.
    2. (b)The hydrophobic tail is on the surface of the cluster, whereas hydrophilic end is in the interior of cluster.
    3. (c)Both hydrophobic tail and hydrophilic end are in the interior of the cluster.
    4. (d)Both hydrophobic tail and hydrophilic end are on the surface of the cluster.
    Show answer

    (a) The hydrophobic tail of the soap molecule is in the interior of the cluster, whereas hydrophilic end is on the surface of the cluster.

    Step-by-step solution →
16. Q96 CBSE 2026
    The ​formula of ​functional ​group for aldehyde ​is ​:

    1. (a)$-\text{COOH}$
    2. (b)$-\text{CHO}$
    3. (c)$-\underset{\stackrel{\Vert }{O}}{C}-$
    4. (d)$-\text{OH}$
    Show answer

    (b) $-\text{CHO}$

    Step-by-step solution →
17. Q97 CBSE 2026
    Which of ​the following ​functional group ​is ​for ​carboxylic acid ​?

    1. (a)$-\text{OH}$
    2. (b)$-\underset{\underset{\text{O}}{\Vert }}{C}-\text{OH}$
    3. (c)$-\underset{\underset{\text{O}}{\Vert }}{C}-$
    4. (d)$-\underset{\underset{\text{O}}{\Vert }}{C}-\text{H}$
    Show answer

    (b) $-\underset{\underset{\text{O}}{\Vert }}{C}-\text{OH}$

    Step-by-step solution →
18. Q98 CBSE 2026
    The hydrocarbons ​with ​general formula ${\text{C}}_n{\text{H}}_{2n}$ ​represents :

    1. (a)alkane
    2. (b)alkene
    3. (c)alkyne
    4. (d)cyclic compounds
    Show answer

    (b) alkene

    Step-by-step solution →
19. Q99 CBSE 2026
    Consider the structures ​‘X’ and ‘Y’ given below : Which of ​the ​following statements are correct ?

    1. (i)‘X’ and ‘Y’ are homologues.
    2. (ii)‘X’ and ‘Y’ have the ​same structural ​formula, but different molecular formula.
    3. (iii)‘X’ and ‘Y’ have ​the same molecular formula, ​but different structural formula.
    4. (iv)‘X’ ​and ‘Y’ are structural isomers.

    1. (a)(i) and (iii)
    2. (b)(i) and (iv)
    3. (c)(ii) and (iv)
    4. (d)(iii) and (iv)
    Show answer

    (d) (iii) and (iv)

    Step-by-step solution →
20. Q100 CBSE 2026
    Which of ​the following ​compounds will ​undergo addition ​reaction ?

    1. (a)${\text{C}}_4{\text{H}}_{10}$
    2. (b)${\text{C}}_4{\text{H}}_8$
    3. (c)${\text{C}}_3{\text{H}}_8$
    4. (d)${\text{CH}}_4$
    Show answer

    (b) ${\text{C}}_4{\text{H}}_8$

    Step-by-step solution →