CBSE Class 10 Science Chapter 4 Carbon and its Compounds Important Questions 2027
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21 questions from Carbon and its Compounds appeared in 7 of the 7 CBSE papers we analysed (2022–2026) — here are the topics that matter, the questions that repeat, and every previous-year question from this chapter.
Key facts
- Chemical Substances - Nature and Behaviour unit — 25 marks in the official syllabus
- Asked in 7 of 7 analysed papers (2022–2026)
- About 3.0 questions per paper (OR alternatives counted separately)
- 5 question patterns repeated across papers
Important topics in Carbon and its Compounds
| # | Topic | Asked in | Importance |
|---|---|---|---|
| 1 | Properties and reactions of ethanol and ethanoic acid | Board 2023Board 2024Board 2025Board 2026Sample 2025 | ★★☆☆☆ |
| 2 | Homologous series | Board 2024Board 2026Sample 2026 | ★☆☆☆☆ |
| 3 | Soaps, detergents and micelle / cleansing action | Board 2023Board 2026Sample 2025 | ★☆☆☆☆ |
| 4 | Combustion, oxidation, addition and substitution reactions | Sample 2025Sample 2026 | ★☆☆☆☆ |
| 5 | Covalent bonding and electron-dot structures | Board 2022Board 2023Board 2024 | ★☆☆☆☆ |
| 6 | Nomenclature and functional groups | Board 2025Board 2026 | ★☆☆☆☆ |
| 7 | Isomers of alkanes | Board 2022 | ★☆☆☆☆ |
Repeated questions from Carbon and its Compounds
1. Ethanol identification and dehydration/reactions
3×Board 2023Board 2024Board 20255 marks
(i) A carbon compound X is a good solvent. On reaction with sodium, X forms two products Y and Z. Z is used to convert vegetable oil into vegetable ghee. Identify and name X, Y and Z. Also write the equation of reaction of X with sodium to justify your answer. (ii) Write chemical equation to show what happens when ethanol: (I) burns in oxygen/air. (II) is heated at 443 K in excess conc. H2SO4. (III) reacts with acidified potassium dichromate.
2. Micelle/cleansing action and soap vs detergent
2×Board 2023Sample 20255 marks
Attempt either option A or B. B. (i) 'A' & 'B' are sodium salts of long-chain carboxylic acid and long chain Sulphonic acid respectively. Which one of A or B will you prefer as a cleansing agent while using underground water (hand pump water)? Give the reason for your answer. (ii) Elaborate on the process of cleansing action. Illustrate micelle with the help of labelled diagram. (iii) Write the chemical equation of the preparation of soap from an ester CH3COOCH3. What is the name of this process?
3. Name structures and write reactions incl. esterification
2×Board 2025Board 20265 marks
(i) How would you name the following: I. CH3-CH2-C(=O)H (i.e. CH3-CH2-CHO); II. CH3-C≡CH. (ii) When ethanol reacts with ethanoic acid in the presence of conc. H2SO4, a substance with sweet smell is produced. Answer the following: I. State the class of compounds to which the sweet smelling compounds belong. II. Write the chemical equation for the reaction. (iii) Why soaps do not produce foam with hard water?
4. Homologous series and melting/boiling trend
2×Board 2024Board 20265 marks
(i) Carbon cannot form C4+ cation and C4- anion. Explain. (ii) Define homologous series of carbon compounds. Why are the melting and boiling points of C4H10 higher than C3H8 or C2H6? (iii) What happens when ethanol is heated with acidified potassium dichromate?
5. Physical properties of covalent compounds
2×Board 2022Board 20241/2 marks
Carbon compounds: (i) are good conductors of electricity. (ii) are bad conductors of electricity. (iii) have strong forces of attraction between their molecules. (iv) have weak forces of attraction between their molecules. The correct statements are: (a) (i) and (ii) (b) (ii) and (iii) (c) (ii) and (iv) (d) (i) and (iii)
Carbon and its Compounds questions by paper
| Paper | Questions | Marks |
|---|---|---|
| Board 2022 | 3 | 8 |
| Board 2023 | 3 | 11 |
| Board 2024 | 3 | 11 |
| Board 2025 | 2 | 10 |
| Sample 2025 | 4 | 14 |
| Board 2026 | 4 | 12 |
| Sample 2026 | 2 | 6 |
Counts include both options of internal-choice (OR) questions.
Previous year questions: Carbon and its Compounds
Board 2026 4 questions
While washing dirty clothes by soap, micelles are formed. Select the correct statement about micelles. (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. (B) The hydrophobic tail is on the surface of the cluster, whereas hydrophilic end is in the interior of cluster. (C) Both hydrophobic tail and hydrophilic end are in the interior of the cluster. (D) Both hydrophobic tail and hydrophilic end are on the surface of the cluster.
Assertion (A): Pure ethanoic acid is also known as glacial acetic acid. Reason (R): Pure ethanoic acid often freezes during winter due to its low melting point of 290 K. (A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A). (B) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A). (C) Assertion (A) is true, but Reason (R) is false. (D) Assertion (A) is false, but Reason (R) is true.
(i) Carbon cannot form C4+ cation and C4- anion. Explain. (ii) Define homologous series of carbon compounds. Why are the melting and boiling points of C4H10 higher than C3H8 or C2H6? (iii) What happens when ethanol is heated with acidified potassium dichromate?
(i) How would you name the following: I. CH3-CH2-C(=O)H (i.e. CH3-CH2-CHO); II. CH3-C≡CH. (ii) When ethanol reacts with ethanoic acid in the presence of conc. H2SO4, a substance with sweet smell is produced. Answer the following: I. State the class of compounds to which the sweet smelling compounds belong. II. Write the chemical equation for the reaction. (iii) Why soaps do not produce foam with hard water?
Sample 2026 2 questions
Assertion (A): C4H8, C4H6 and C4H10 are members of the same homologous series. Reason (R): C4H8, C4H6, C3H4, C3H6, C2H4, C2H2 are unsaturated hydrocarbons. Options: A. Both A and R are true, and R is the correct explanation of A. B. Both A and R are true, and R is not the correct explanation of A. C. A is true but R is false. D. A is false but R is true.
A hydrocarbon with the formula CxHy undergoes complete combustion as shown in the following equation: 2CxHy + 9O2 -> 6CO2 + 6H2O. (a) What are the values of 'x' and 'y'? (b) Give the chemical (IUPAC) name of the hydrocarbon. (c) Draw its electron dot structure. (d) Name the alcohol which on heating with conc. H2SO4 will produce the above hydrocarbon CxHy. (e) Write a balanced chemical equation for the reaction of CxHy with hydrogen gas in presence of Nickel.
Board 2025 2 questions
(i) Draw two isomeric structures of Butene (C4H8). (ii) Name the following compounds: (I) CH3-CH2-CH2-Cl (a chain of three carbons each fully H-saturated with a Cl on the end carbon); (II) CH3-CH2-CO-CH3 (a four-carbon chain with a C=O double bond on the third carbon). (iii) Write the chemical equations for the following reactions. Mention one essential condition each for these reactions to take place. (I) Ethanol undergoes complete oxidation (II) Propene undergoes hydrogenation (III) Ethanoic acid reacts with ethanol.
(i) A carbon compound X is a good solvent. On reaction with sodium, X forms two products Y and Z. Z is used to convert vegetable oil into vegetable ghee. Identify and name X, Y and Z. Also write the equation of reaction of X with sodium to justify your answer. (ii) Write chemical equation to show what happens when ethanol: (I) burns in oxygen/air. (II) is heated at 443 K in excess conc. H2SO4. (III) reacts with acidified potassium dichromate.
Sample 2025 4 questions
[Case context: an integrated reaction scheme linking chlor-alkali electrolysis and esterification, with boxed compounds A, X, Y, Z, M, P, Q, R. (1) A + H2O --electrolysis--> X(caustic soda) + Y(anode) + Z(cathode); (2) A(molten) --electrolysis--> M(cathode) + Y(anode); (3) M + CH3COOH -> P + Z; (4) CH3COOH + Q --(conc. H2SO4)--> R; (5) R + X -> P + Q.] A. Derive the names of A, Y, Z, M, P & R.
[Case context: integrated chlor-alkali/esterification reaction scheme with boxed compounds A, X, Y, Z, M, P, Q, R.] Attempt either subpart B or C. B. Improvise an activity to test Z.
Attempt either option A or B. A. (i) "Keerthi thinks that Substitution reaction occurs in saturated Hydrocarbons, on the contrary Krishi thinks, it occurs in unsaturated Hydrocarbons." Justify with valid reasoning whose thinking is correct. (ii) "Methane and Propane and their Isomers are used as fuels" Comment. Draw the electron dot structure of the immediate lower homologue of Propane. Give any two characteristics of homologues of a given homologous series. (iii) A mixture of oxygen and ethyne is burnt for welding. Can you predict why a mixture of ethyne and air is not used?
Attempt either option A or B. B. (i) 'A' & 'B' are sodium salts of long-chain carboxylic acid and long chain Sulphonic acid respectively. Which one of A or B will you prefer as a cleansing agent while using underground water (hand pump water)? Give the reason for your answer. (ii) Elaborate on the process of cleansing action. Illustrate micelle with the help of labelled diagram. (iii) Write the chemical equation of the preparation of soap from an ester CH3COOCH3. What is the name of this process?
Board 2024 3 questions
Carbon compounds: (i) are good conductors of electricity. (ii) are bad conductors of electricity. (iii) have strong forces of attraction between their molecules. (iv) have weak forces of attraction between their molecules. The correct statements are: (a) (i) and (ii) (b) (ii) and (iii) (c) (ii) and (iv) (d) (i) and (iii)
(i) Define a homologous series of carbon compounds. (ii) Why is the melting and boiling points of C4H8 higher than that of C3H6 or C2H4? (iii) Why do we NOT see any gradation in chemical properties of a homologous series compounds? (iv) Write the name and structures of (i) aldehyde and (ii) ketone with molecular form C3H6O.
(i) Write the name and structure of an organic compound 'X' having two carbon atoms in its molecule and its name is suffixed with '-ol'. (ii) What happens when 'X' is heated with excess concentrated sulphuric acid at 443 K? Write chemical equation stating the conditions for the reaction. Also state the role played by concentrated sulphuric acid in the reaction. (iii) Name and draw the electron dot structure of hydrocarbon produced in the above reaction.
Board 2023 3 questions
Consider the structures of the three cyclic carbon compounds A, B and C given below and select the correct option from the following: (a) A and C are isomers of hexane and B is benzene. (b) A is an isomer of hexane, B is benzene and C is an isomer of hexene. (c) A is a saturated cyclic hydrocarbon and B and C are unsaturated cyclic hydrocarbons. (d) A is cyclohexane and B and C are the isomers of benzene. [A is a six-membered ring with each carbon bonded to two hydrogens (cyclohexane); B and C are six-membered rings with alternate double bonds and one hydrogen per carbon (benzene / Kekule structures).]
A saturated organic compound 'A' belongs to the homologous series of alcohols. On heating 'A' with concentrated sulphuric acid at 443 K, it forms an unsaturated compound 'B' with molecular mass 28 u. The compound 'B' on addition of one mole of hydrogen in the presence of Nickel, changes to a saturated hydrocarbon 'C'. (i) Identify A, B and C. (ii) Write the chemical equations showing the conversion of A into B. (iii) What happens when compound C undergoes combustion? (iv) State one industrial application of hydrogenation reaction. (v) Name the products formed when compound A reacts with sodium.
(i) With the help of diagram, show the formation of micelles, when soap is applied on oily dirt. (ii) Take two test tubes X and Y with 10 mL of hard water in each. In test tube 'X', add few drops of soap solution and in test tube 'Y' add a few drops of detergent solution. Shake both the test tubes for the same period. (1) In which test tube the formation of foam will be more? Why? (2) In which test tube is a curdy solid formed? Why?
Board 2022 3 questions
(a) Write the molecular formula of the following carbon compounds: (i) Methane (ii) Propane. (b) Carbon compounds have low melting and boiling points. Why?
Draw two different possible structures of a saturated hydrocarbon having four carbon atoms in its molecule. What are these two structures of the hydrocarbon having same molecular formula called? Write the molecular formula and the common name of this compound. Also write the molecular formula of its alkyne.
(i) Write the molecular formula of benzene and draw its structure. (ii) Write the number of single and double covalent bonds present in a molecule of benzene. (iii) Which compounds are called alkynes?
Frequently asked questions
What are the most important topics in CBSE Class 10 Science Chapter 4 Carbon and its Compounds?
By how often and how recently they were asked: Properties and reactions of ethanol and ethanoic acid; Homologous series; Soaps, detergents and micelle / cleansing action.
How many marks does Carbon and its Compounds carry in the CBSE Class 10 Science exam?
Carbon and its Compounds is part of the Chemical Substances - Nature and Behaviour unit, which carries 25 marks in the official syllabus. In the analysed papers it had about 3.0 questions per paper.
Do questions from Carbon and its Compounds repeat in board exams?
Yes — 5 question patterns from this chapter appeared in two or more past board or official sample papers. They are listed on this page with the years they were asked.