Carbon and Its Compounds — Class 10 MCQs with Answers

Carbon and Its Compounds — important questions & MCQs with answers (Class 10 Science (Chemistry))

6 solved questions from this chapter's difficulty levels, each with its answer and explanation. Tap an option to check yourself.

0 of 6 answered

1. Q1 of 6Easy

   Valency of carbon is:

   A2B4C6D8
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   Answer: 4

   Explanation: Carbon (Z=6) has 4 electrons in its outermost shell, so it shares 4 electrons to complete its octet — giving it a valency of 4, not 2 like oxygen or 6 like sulfur.

2. Q2 of 6Easy

   Methane formula:

   ACH₂BC₂H₆CCH₄DCH₃
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   Answer: CH₄

   Explanation: Methane is the first member of the alkane series CₙH₂ₙ₊₂; for n=1 that gives CH₄, since CH₂ or CH₃ can't satisfy carbon's valency of 4.

3. Q3 of 6Medium

   Which property is shared by diamond and graphite?

   ASame chemical compositionBSame hardnessCSame lustreDSame conductivity
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   Answer: Same chemical composition

   Explanation: Diamond and graphite are allotropes: same element, pure carbon, but different atomic arrangements — which is why hardness, lustre and conductivity differ despite identical composition.

4. Q4 of 6Medium

   Assertion (A): Members of a homologous series show a gradation in physical properties. Reason (R): The chemical properties of a homologous series are decided by the functional group.

   ABoth A and R are true and R is the correct explanation of ABBoth A and R are true but R is not the correct explanation of ACA is true but R is falseDA is false but R is true
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   Answer: Both A and R are true but R is not the correct explanation of A

   Explanation: Both are true. The gradation in physical properties is due to the increase in molecular mass, not the functional group, so R does not explain A.

5. Q5 of 6Hard

   Which is the formula of an alcohol?

   AC₂H₅OHBCH₃COOHCCH₃CHODCH₃COCH₃
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   Answer: C₂H₅OH

   Explanation: C₂H₅OH carries the −OH hydroxyl group bonded directly to a saturated carbon chain, the defining feature of an alcohol — the other options carry −COOH, −CHO or C=O groups instead.

6. Q6 of 6Hard

   Assertion (A): The molecular masses of CH₃OH and C₂H₅OH differ by 14 u. Reason (R): Successive members of a homologous series differ by a –CH₂– unit.

   ABoth A and R are true and R is the correct explanation of ABBoth A and R are true but R is not the correct explanation of ACA is true but R is falseDA is false but R is true
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   Answer: Both A and R are true and R is the correct explanation of A

   Explanation: Both are true. The two alcohols differ by one –CH₂– unit, which has a mass of 12 + 2 × 1 = 14 u (32 u and 46 u), so R explains A.

Carbon and Its Compounds notes: key concepts (Class 10 Science (Chemistry))

Carbon forms more compounds than all other elements combined, because it catenates and has a valency of four. This chapter covers its allotropes, covalent bonding, hydrocarbons, functional groups, homologous series, IUPAC naming and the chemistry of ethanol and ethanoic acid.

Covalent bond

A bond formed by the SHARING of electron pairs between atoms, which is how carbon achieves a stable octet.

Properties of covalent compounds

Generally low melting and boiling points and poor conductors, since the molecules are neutral and there are no free ions or electrons.

Catenation

Carbon's ability to bond with other carbon atoms forming long chains, branches and rings — the main reason for the vast number of carbon compounds.

Tetravalency

Carbon has four valence electrons and forms four bonds, allowing it to combine with many other atoms in stable arrangements.

Allotropes of carbon

Different physical forms of the same element: diamond (rigid three-dimensional network, hardest known), graphite (slippery layers that conduct) and fullerenes such as C-60.

Saturated and unsaturated hydrocarbons

Alkanes contain only single bonds and are saturated; alkenes and alkynes contain double and triple bonds and are unsaturated.

Structural isomerism

Compounds with the same molecular formula but different structural arrangements, first appearing at butane (C₄H₁₀).

Functional group

An atom or group replacing a hydrogen and giving the molecule its characteristic properties — alcohol, aldehyde, ketone, carboxylic acid and halogen.

Homologous series

A family of compounds with the same functional group and general formula, in which successive members differ by a −CH₂− unit and 14 u.

IUPAC naming

Systematic naming from the number of carbons (meth-, eth-, prop-, but-) plus a suffix or prefix for the functional group.

Combustion

Carbon compounds burn in air releasing heat and light; saturated compounds give a clean blue flame, unsaturated ones a sooty yellow flame.

Oxidation and oxidising agents

Alcohols are oxidised to carboxylic acids by alkaline potassium permanganate or acidified potassium dichromate.

Addition and substitution reactions

Unsaturated compounds undergo addition, as in hydrogenation with a nickel catalyst; saturated compounds undergo substitution in sunlight.

Ethanol

A liquid alcohol used in medicines and as a fuel; it reacts with sodium releasing hydrogen and dehydrates to ethene with hot concentrated sulphuric acid.

Ethanoic acid

Acetic acid, whose 5-8% solution is vinegar; it freezes in cold climates to glacial acetic acid and reacts with carbonates to give CO₂.

Esterification and saponification

An acid and an alcohol give a sweet-smelling ester; hydrolysing an ester with alkali gives back the alcohol and a soap.