Important Questions for CBSE Class 10 Science Chapter 4: Understanding the basics of carbon compounds is essential for Class 10 students. Chapter 4 focuses on covalent bonding, the versatile nature of carbon, functional groups, and important reactions such as combustion, oxidation, and substitution.
Practising Carbon and Its Compounds Class 10 important questions helps students improve clarity, strengthen fundamentals, and score better in exams. This will help you access clear, well-selected, important questions to build strong concepts and boost exam preparation efficiently.
Carbon and Its Compounds Class 10 Important Questions With Answers
Practising Carbon and Its Compounds Class 10 Important Questions with Answers helps students understand bonding, functional groups, and key reactions clearly. These solved questions improve accuracy, strengthen concepts, and boost overall Science exam performance.
1. Write the molecular formula of first two members of homologous series having functional group —OH.
Sol..
(1) CH3OH (Methanol)
(2) C2H5OH (Ethanol)
2. Write the molecular formula of 2nd and 3rd member of the homologous series whose first member is ethyne
Sol.
(1) HC C—CH3 (Propyne)
(2) HC C—CH2—CH3 (1-Butyne)
3. Name the following compounds:
Sol.
a. Ethanol
b. Ethanal
4. A colourless gas 'X' has a formula C3H6. It decolourises bromine water. Write the chemical formula of 'X'.
Sol. CH2 = CH—CH3, Propene
5. List two characteristic features of carbon, which, when put together, give rise to a number of carbon compounds.
Sol:
(a) Tetravalency
(b) Catenation
6. Explain why washing clothes with hard water is not effective.
Sol. Soap reacts with Ca2+ and Mg2+ ions present in hard water to form scum.
7. What happens when a small piece of sodium is dropped into ethanol?
Sol. Sodium ethoxide and H2 gas is formed
2C2H5OH + 2Na → 2C2H5ONa + H2
8. What will you observe on adding a 5% alkaline KMnO4 solution drop by drop to some warm ethanol taken in a test tube? Write the name of the compound formed during the above chemical reaction.
Sol. The purple colour of KMnO4 decolourises and ethanoic acid will be formed. 
9. Write the electron dot structure of ethene molecule (C2H4).
10. Name the following compound:
Sol. 1-Hexyne
11. Name the carbon compound which, on heating with an excess of conc. H2SO4 at 443 K gives ethene.
12.
a. Write chemical name and formula of vinegar?
b. Describe with a chemical equation what happens when sodium reacts with ethanol.
13. State reasons to explain why covalent compounds:
a. Are bad conductors of electricity?
b. have low melting and boiling points?
Sol.
a. Covalent compounds do not form ions, hence they are bad conductor of electricity.
b. Covalent compounds have weak intermolecular forces of attraction; therefore, they have low melting and boiling points.
14. What is a homologous series? Write the name and draw the structure of the second member of the alkene series.
Sol. The series of organic compounds having the same functional group and similar chemical properties is called a homologous series.
15. List two characteristics of covalent compounds.
Sol.
(i) They have low melting and boiling points.
(ii) They do not conduct electricity.
16. The structural formula of an ester is
Write the structural formula of the corresponding alcohol and acid.
17. Name the functional groups of the following compounds:
Sol.
a. Carboxylic acid
b. Ester
c. Alcohol
d. Halogen
18. What is hydrogenation? What is its industrial application?
Sol. Hydrogenation is a process of adding hydrogen to unsaturated compounds in the presence of a catalyst like nickel, to form saturated hydrocarbons. Industrially, it is used to convert vegetable oils to vegetable ghee.
19. How do the melting and boiling points of the hydrocarbons change with an increase in molecular mass?
Sol. Melting and boiling point of the hydrocarbons increase with increase in molecular mass because surface area increases which results an increase in vander Waal's forces of attraction between molecules.
20. Write a chemical test to distinguish between ethanol and ethanoic acid.
or
How would you distinguish experimentally between ethanol and ethanoic acid with the help of sodium hydrogen carbonate? Write the chemical equation for the reaction involved.
Sol. Add NaHCO3 to each of them separately. Ethanol will 3 not react with NaHCO3, but ethanoic acid reacts with NaHCO3 to give brisk effervescence due to CO2 formation.
21. List four characteristics of a homologous series.
Sol
a. All members are derived from same general formula.
b. All members have same functional group.
c. Each successive member differ by —CH2 unit.
d. All members can be prepared by same methods of preparation.
22. What are soaps? Why do they form scum with hard water?
Sol. Soaps are sodium or potassium salts of fatty acids e.g. sodium stearate. They react with Ca2+ and Mg2+ ions in hard water to form calcium and magnesium salt of fatty acids which are insoluble in water and called scum.
23. Explain the action of soap in removing an oily spot from a piece of cloth.
Sol. Cleansing action of soap: Soap has ionic ends, which are hydrophilic, interact with water, while the carbon chain is hydrophobic, interacts with oil, grease. The soap molecules orient themselves in a cluster in which hydrophobic tails are inside the cluster, and ionic ends face outside. These clusters are called micelles. These attract oil, which is washed away by water.
24. Draw electron dot structures of
(i) C2H4
ii) C2H5O
25. A compound X on heating with excess of conc. H2SO4 at 443 K gives an unsaturated compound Y. X also reacts with sodium metal to evolve a colourless gas Z. Identify X, Y and Z. Write the equations of the chemical reactions involved and also write the role of conc. sulphuric acid in the reaction.
26. An aldehyde as well as ketone can be represented by the same molecular formula say C3H6O. Write their structures and name them. State the relationship between two in language of science.
Sol. They are functional isomers
27. Complete the following equations:
28. Distinguish between esterification and saponification reactions with the help of equations for each. State one use of each (i) esters and (ii) saponification process.
Sol. Esterification
Esters are used in synthetic flavours, perfumes, etc. The saponification process is used for the manufacture of soaps.
29. What are hydrocarbons? Write the general formula of
(a) saturated hydrocarbons
(b) unsaturated hydrocarbons, and draw the structure of one hydrocarbon of each type.
Sol. Hydrocarbons are compounds of carbon and hydrogen only.
30. What are covalent and ionic compounds? Why covalent component are different from ionic compounds? List three characteristic properties of each.
Sol. Those compounds in which bonds are formed by sharing of electrons are covalent compounds. While ionic compounds are formed by complete transfer of electrons.
31. Why should we prefer vegetable oils over animal fats for cooking food? Give a balanced chemical equation for reaction of hydrogenation of vegetable oils. Name the catalyst in the reaction
Sol. Vegetable oils are unsaturated and do not lead to formation of cholesterol. Animals fats are saturated lead to formation of cholesterol which can be deposited in arteries.
32. What are micelles? Why does it form when soap is added to water? Will a micelle be formed in other solvents, such as ethanol, also? State briefly how the formation of micelles helps to clean the clothes having oily spots.
Sol. Micelles are cluster of molecules in which hydrophobic tails are inside the cluster and the ionic ends are at the surface of clusters. Soap molecules when dissolved in water they form a cluster due to hydrophobic part of molecules orient themselves away from water. So, they arrange towards inside of the cluster while hydrophilic part remain outside of cluster. Because the oily dirt will be collected in centre of micelle which is rinsed away by water. No, micelles will not be formed in alcohol.
33.
a. Differentiate between soap and detergent.
b. Explain why soaps form scum with water, whereas detergents do not.
b. Sodium salts of fatty acids (soaps) react with Ca2+ and Mg2+ ions in hard water to form insoluble salts called scum. Detergents form soluble salts with Ca2+ and Mg2+
34. Give reasons for the following:
a. Element carbon forms compounds mainly by covalent bonding.
b. Diamond has a high melting point.
c. Graphite is good conductor of electricity.
d. Acetylene burns with sooty flame.
e. Kerosene does not decolourise bromine water whereas cooking oil does.
Sol.
a. It is because carbon can neither lose 4 electrons nor gain 4 electrons. It can share four electrons to form covalent bonds.
b. Diamond has strong C—C bonds and compact 3-D structure in which one carbon
atom is covalently bonded to other four carbon atoms therefore, has high melting
Point.
c. In graphite, one carbon atom is bonded to other three carbon atoms. Remaining one
electron on each carbon is free to move due to which graphite conducts electricity.
d. Acetylene has high carbon content; therefore, partial oxidation causes it to bum with sootyor smoky flame.
e. Kerosene is a saturated compound; therefore, it does not decolourise bromine water.
35. What are detergents chemically? List two merits and two demerits of using detergents for cleansing. State the reason for the suitability of detergents for washing, even in the case of water having calcium and magnesium ions.
Sol. Detergents are sodium or potassium salts of sulphonic acids or ammonium salts of chlorides or bromides ions.
Merits:
They are more effective than soaps.
They work well even with hard water.
Demerits:
a. They are expensive.
b. Some of them create water pollution.
36. Compound 'X' works well with hard water. It is used for making shampoos & products for cleaning clothes. Compound 'X' is not 100% biodegradable and causes water pollution. Compound 'Y' does not work well with hard water and it is 100% biodegradable and does not cause water pollution.
(i) Identify compound 'X'.
(a) Detergent
(b) Soap
(c) Washing soda
(d) Baking soda
Sol: (a) X is detergent.
(ii) Identify Y.
(a) Washing soda
(b) Soap
(c) Detergent
(d) Sulfates
Sol: (b) Y is soap.
37. The molecular formula of an organic compound ‘X’ is C2H6O. It is an active ingredient of all alcoholic drinks. It is also sed in medicines such as tincture of iodine, cough syrups. A small piece of Na is dropped into the test tube containing ‘X’, as a result new compound ‘Y’ is formed with the evolution of colourless and odorless gas.
(i) Identity the compound 'X'.
(a) Ethanol
(b) Ethanoic acid
(c) Methanol
(d) Diethylether
Sol: (a) Ethanol
(ii) Identify the compound 'Y'.
(a) CH3COOH
(b) CH3CH2OH
(c) CH3CH2ONa
(d) CH3CH2CH2ONa
Sol: (c) CH3CH2ONa
(iii) Name the gas evolved with compound 'Y'.
(a) H2 (b) CO2
(c) Cl2 (d) N2
Sol: (a) H2
38. The molecular formula of an organic compound 'P' is C2H6O, which is used as an antifreeze. Compound 'P' on oxidation gives a compound 'Q' which gives effervescence on treatment with a baking soda solution.
(i) Identify compound 'P'.
(a) Methanol
(b) Ethanol
(c) Ethanoic acid
(d) Ethyl methyl ester
Sol: (b) Ethanol
(ii) Identify compound 'Q'.
(a) Propanoic acid
(b) Ethanoic acid
(c) Methanol
(d) Pentanol
Sol: (b) Ethanoic acid
(iii) Which gas is formed when Q reacts with baking soda solution?
(a) Nitrogen
(b) Hydrogen
(c) Carbon dioxide
(d) Chlorine
Sol: (c) Carbon dioxide
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