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Class 10 · Science · Chapter 4: Carbon and its Compounds

BSEB Class 10 Science Chapter 4: Objective Questions (MCQ) with Answers

Bihar Board · NCERT · CBSE

All 59 objective questions (MCQ) of this chapter — solve first, then tap “Show answer”. Each question shows its source label: «BSEB 2025 · board paper» = verified from the official board paper; «Board-style (practice)» = Study With Me's own practice questions.

← Chapter 4: Carbon and its Compounds — full notes, video, questions

1Check

How many electrons are in the outer shell of carbon?

  1. (A) Two
  2. (B) Four
  3. (C) Six
  4. (D) Eight
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Correct answer: (B) Four

There are four electrons in the outer shell, so the valency is four.

2Check

Why does carbon not easily form a C4+ ion?

  1. (A) It has no electrons at all
  2. (B) Removing four electrons costs a lot of energy
  3. (C) It is a metal
  4. (D) Its valency is one
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Correct answer: (B) Removing four electrons costs a lot of energy

Removing four electrons costs a lot of energy, so carbon shares.

3Check

In diamond, one carbon atom is bonded to how many carbons?

  1. (A) Two
  2. (B) Three
  3. (C) Four
  4. (D) Six
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Correct answer: (C) Four

In diamond each carbon is bonded to four other carbons.

4Check

The shape of C60 is like which object?

  1. (A) A long rod
  2. (B) A football
  3. (C) A stack of sheets
  4. (D) Only a single ring
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Correct answer: (B) A football

In C60 the carbon atoms are arranged like a football.

5Check

Which of the following is unsaturated?

  1. (A) Methane
  2. (B) Ethane
  3. (C) Ethene
  4. (D) Propane
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Correct answer: (C) Ethene

Ethene C2H4 has a carbon-carbon double bond.

6Check

What is the chain CH3OH, C2H5OH, C3H7OH and C4H9OH called?

  1. (A) Isomers
  2. (B) A homologous series
  3. (C) Allotropes
  4. (D) A micelle
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Correct answer: (B) A homologous series

The same functional group and a gap of CH2 — this is a homologous series.

7Check

The functional group in butanone is —

  1. (A) Carboxylic acid
  2. (B) Aldehyde
  3. (C) Ketone
  4. (D) Alcohol
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Correct answer: (C) Ketone

Butanone is a four-carbon ketone.

8Check

The correct name of CH3CH2Br is —

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

Two carbons and a −Br prefix: bromoethane.

9Check

The bottom of a vessel is turning black on the outside. This means —

  1. (A) The food is fully cooked
  2. (B) The fuel is burning incompletely
  3. (C) The fuel is wet
  4. (D) The fuel is burning completely
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Correct answer: (B) The fuel is burning incompletely

A blackened base is the sign of incomplete combustion. Fuel is being wasted.

10Check

In Activity 4.4, when do you get a yellow sooty flame?

  1. (A) When the air hole is fully open
  2. (B) When the air hole is closed
  3. (C) Only when water is added
  4. (D) When the burner is off
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Correct answer: (B) When the air hole is closed

When the air hole is closed, oxygen is short and the flame is yellow and sooty.

11Check

Why is oxygen mixed with ethyne for welding, instead of air?

  1. (A) Nitrogen in air cools the flame and combustion stays incomplete
  2. (B) Ethyne does not burn in oxygen at all
  3. (C) Air turns ethyne into an acid
  4. (D) Oxygen increases the soot
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Correct answer: (A) Nitrogen in air cools the flame and combustion stays incomplete

Air has less oxygen. The mixture burns incompletely, soot forms, and the temperature is not enough for welding.

12Check

In Activity 4.5, alkaline KMnO4 changes ethanol into which compound?

  1. (A) Methane
  2. (B) Ethene
  3. (C) Ethanoic acid
  4. (D) An ester
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Correct answer: (C) Ethanoic acid

Ethanol is oxidised to ethanoic acid.

13Check

The industrial catalyst for adding hydrogen to a vegetable oil is —

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

In the presence of a nickel catalyst an unsaturated oil adds hydrogen and becomes a saturated fat.

14Check

Which gas is released from ethanol and sodium in Activity 4.6?

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

The gas is hydrogen. The pop is its test.

15Check

Heating ethanol at 443 K with concentrated H2SO4 gives —

  1. (A) Methane
  2. (B) Ethene
  3. (C) Ethane
  4. (D) Glucose
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Correct answer: (B) Ethene

Dehydration gives ethene and water.

16Check

Pure ethanoic acid is called glacial because —

  1. (A) it is blue
  2. (B) it often freezes at 290 K
  3. (C) it is a base
  4. (D) it contains no carbon
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Correct answer: (B) it often freezes at 290 K

The melting point is 290 K, so in the cold it freezes like ice.

17Check

In Activity 4.8, the sweet smell after pouring into water belongs to which compound?

  1. (A) Methane
  2. (B) An ester
  3. (C) Hydrogen
  4. (D) Soot
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Correct answer: (B) An ester

The sweet smell is of ethyl ethanoate, which is an ester.

18Check

In a micelle, which way does the soap tail point?

  1. (A) Outward, toward water
  2. (B) Inside the oil drop
  3. (C) Up into the air
  4. (D) Only onto the glass
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Correct answer: (B) Inside the oil drop

The hydrophobic tail stays inside the oil and the ionic head faces outward toward water.

19Check

In Activity 4.11, more lather forms in which water?

  1. (A) Hard water
  2. (B) Distilled or rain water
  3. (C) Equally in both
  4. (D) Only in oil
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Correct answer: (B) Distilled or rain water

More lather forms in distilled water or rain water. Hard water gives a white precipitate.

20BSEB 2025 · board paper · Q41 · page 151 mark

The molecular formula of benzene is—

  1. (A) C2H2
  2. (B) C2H4
  3. (C) CH4
  4. (D) C6H6
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Correct answer: (D) C6H6

Benzene is a ring of six carbons with alternate single and double bonds — C6H6 (lesson 3, Fig. 4.10). C₂H₂ is ethyne, C₂H₄ ethene, CH₄ methane.

21BSEB 2025 · board paper · Q42 · page 151 mark

Which bond is formed between two hydrogen atoms?

  1. (A) Triple bond
  2. (B) Double bond
  3. (C) Single bond
  4. (D) None of these
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Correct answer: (C) Single bond

Each H has one electron; together they form one shared pair — a single bond, H—H (lesson 1, Fig. 4.1, 4.2).

22BSEB 2025 · board paper · Q45 · page 161 mark

Which of the following organic compounds is the most reactive?

  1. (A) C2H6
  2. (B) CH4
  3. (C) C3H8
  4. (D) C2H4
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Correct answer: (D) C2H4

C₂H₆, CH₄ and C₃H₈ are saturated alkanes. C2H4 (ethene) has a C=C double bond — unsaturated compounds are more reactive than saturated ones (lesson 3).

23BSEB model paper 2026 (not the annual exam) · Q43 · page 151 mark

The functional group >CO is called—

  1. (A) Aldehyde group
  2. (B) Ether group
  3. (C) Alcohol group
  4. (D) Carbonyl group
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Correct answer: (D) Carbonyl group

>C=O is the carbonyl group; between two carbons it is a ketone (suffix ‘-one’), e.g. propanone (lesson 4, Table 4.3). The aldehyde group is —CHO and the alcohol group —OH.

24BSEB model paper 2026 (not the annual exam) · Q44 · page 151 mark

Which gas is used in welding?

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

Ethyne (C2H2) is burnt with oxygen — complete combustion gives a very high temperature (lesson 5; NCERT in-text question, page 71).

25BSEB model paper 2026 (not the annual exam) · Q45 · page 151 mark

Carbon belongs to which group of the periodic table?

  1. (A) 3
  2. (B) 6
  3. (C) 13
  4. (D) 14
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Correct answer: (D) 14

Carbon (2, 4) has 4 electrons in its outer shell — group 14 of the modern periodic table. Note: 6 is carbon's atomic number, not its group.

26BSEB model paper 2026 (not the annual exam) · Q46 · page 161 mark

How many covalent bonds are there between the carbon atoms in ethyne?

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

Ethyne H—C≡C—H has a triple bond between the two carbons — 3 shared electron pairs (lesson 3). (In the paper's English options, (D) is misprinted as 3; the Hindi options read 4.)

27Book-based · 4 (परिचय) · page 581 mark

How much carbon does the earth's crust have in the form of minerals?

  1. (A) 0.02%
  2. (B) 0.03%
  3. (C) 2%
  4. (D) 3%
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Correct answer: (A) 0.02%

Book: the crust has only 0.02% carbon; the atmosphere has 0.03% CO₂.

28Book-based · 4.1 · page 581 mark

In Table 4.1, which compound melts at 290 K?

  1. (A) Methane
  2. (B) Ethanol
  3. (C) Acetic acid
  4. (D) Chloroform
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Correct answer: (C) Acetic acid

Acetic acid 290 K / 391 K; ethanol 156 K / 351 K; methane 90 K / 111 K; chloroform 209 K / 334 K.

29Book-based · 4.1 · page 591 mark

Why does carbon not form the C⁴⁻ ion?

  1. (A) It has no electrons
  2. (B) Six protons cannot hold ten electrons
  3. (C) It is a metal
  4. (D) It is a gas
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Correct answer: (B) Six protons cannot hold ten electrons

Book: it is difficult for a nucleus with six protons to hold on to ten electrons (four extra).

30Book-based · 4.1 · page 601 mark

How many shared electron pairs are in a nitrogen molecule?

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

Each N contributes three electrons → 3 shared pairs = a triple bond (Fig. 4.4).

31Book-based · 4.1 (और जानें) · page 611 mark

In graphite, each carbon is bonded to how many carbons?

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

Graphite: three carbons in one plane, hexagonal array; diamond: four.

32Book-based · 4.2 · page 621 mark

Silicon forms chains with hydrogen of up to how many atoms?

  1. (A) 2–3
  2. (B) 7–8
  3. (C) 20–30
  4. (D) unlimited
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Correct answer: (B) 7–8

Book: silicon forms chains of up to seven or eight atoms, but these compounds are very reactive.

33Book-based · 4.2.2 · page 651 mark

The formula of cyclohexane is—

  1. (A) C6H6
  2. (B) C6H12
  3. (C) C6H14
  4. (D) C5H12
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Correct answer: (B) C6H12

A ring of six C, all single bonds → C6H12 (Fig. 4.9). C₆H₆ is benzene, C₆H₁₄ hexane.

34Book-based · 4.2.4 · page 661 mark

The difference in molecular mass of two successive members of a homologous series is—

  1. (A) 12 u
  2. (B) 14 u
  3. (C) 16 u
  4. (D) 18 u
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Correct answer: (B) 14 u

Difference —CH₂— = 12 + 2×1 = 14 u.

35Book-based · 4.3.2 · page 711 mark

Which of these is an oxidising agent?

  1. (A) Alkaline potassium permanganate
  2. (B) Sodium chloride
  3. (C) Ethanol
  4. (D) Nickel
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Correct answer: (A) Alkaline potassium permanganate

Alkaline KMnO₄ and acidified K₂Cr₂O₇ convert alcohols to acids — oxidising agents.

36Book-based · 4.4.1 · page 721 mark

Heating ethanol at 443 K with excess conc. H₂SO₄ gives—

  1. (A) ethane
  2. (B) ethene
  3. (C) ethyne
  4. (D) methane
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Correct answer: (B) ethene

C2H5OH 443 K, conc. H2SO4→ C2H4 + H2O — dehydration.

37Book-based · 4.4.2 · page 731 mark

Vinegar is what percentage solution of acetic acid in water?

  1. (A) 1–2%
  2. (B) 5–8%
  3. (C) 20–30%
  4. (D) 100%
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Correct answer: (B) 5–8%

Book: a 5–8% solution = vinegar, a preservative in pickles.

38Book-based · 4.5 · page 761 mark

Detergents are generally—

  1. (A) sodium salts of long-chain carboxylic acids
  2. (B) sodium salts of sulphonic acids
  3. (C) calcium salts
  4. (D) esters
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Correct answer: (B) sodium salts of sulphonic acids

Detergents: sodium salts of sulphonic acids or ammonium salts with chloride/bromide ions. (a) is soap.

39NCERT exercise · Q11 mark

Ethane, with the molecular formula C₂H₆, has

  1. (A) 6 covalent bonds
  2. (B) 7 covalent bonds
  3. (C) 8 covalent bonds
  4. (D) 9 covalent bonds
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Correct answer: (B) 7 covalent bonds

1 C—C + 6 C—H = 7 covalent bonds.

40NCERT exercise · Q21 mark

Butanone is a four-carbon compound with the functional group

  1. (A) carboxylic acid
  2. (B) aldehyde
  3. (C) ketone
  4. (D) alcohol
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Correct answer: (C) ketone

Suffix ‘-one’ = ketone (>C=O).

41NCERT exercise · Q31 mark

While cooking, if the bottom of the vessel is getting blackened on the outside, it means that

  1. (A) the food is not cooked completely
  2. (B) the fuel is not burning completely
  3. (C) the fuel is wet
  4. (D) the fuel is burning completely
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Correct answer: (B) the fuel is not burning completely

Soot = incomplete combustion; the air holes are blocked and fuel is wasted.

42Board-style (practice)1 mark

The number of covalent bonds in an ethane molecule is —

  1. (A) 6
  2. (B) 7
  3. (C) 8
  4. (D) 9
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Correct answer: (B) 7

Ethane has 7 covalent bonds.

43Board-style (practice)1 mark

The amount of carbon in the crust is about —

  1. (A) 0.02%
  2. (B) 2%
  3. (C) 20%
  4. (D) 78%
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Correct answer: (A) 0.02%

Carbon in the crust is about 0.02%.

44Board-style (practice)1 mark

The carbon allotrope that conducts electricity is —

  1. (A) Diamond
  2. (B) Graphite
  3. (C) Coal only
  4. (D) Lime
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Correct answer: (B) Graphite

Graphite conducts. Diamond does not.

45Board-style (practice)1 mark

C60 is called —

  1. (A) Diamond
  2. (B) A fullerene
  3. (C) An alkane
  4. (D) An ester
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Correct answer: (B) A fullerene

C60 is a fullerene.

46Board-style (practice)1 mark

The general formula of an alkane is —

  1. (A) CnH2n
  2. (B) CnH2n+2
  3. (C) CnH2n−2
  4. (D) CnH2n+1
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Correct answer: (B) CnH2n+2

Alkanes are CnH2n+2.

47Board-style (practice)1 mark

The number of structural isomers of pentane is —

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

Pentane has three structural isomers.

48Board-style (practice)1 mark

The mass of the homologous gap is —

  1. (A) 2 u
  2. (B) 12 u
  3. (C) 14 u
  4. (D) 16 u
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Correct answer: (C) 14 u

The gap is 14 u.

49Board-style (practice)1 mark

Propanone is —

  1. (A) An alcohol
  2. (B) An aldehyde
  3. (C) A ketone
  4. (D) An acid
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Correct answer: (C) A ketone

Propanone is a three-carbon ketone.

50Board-style (practice)1 mark

Which of these is not a cause of a sooty flame?

  1. (A) An unsaturated compound
  2. (B) A short supply of air
  3. (C) A saturated compound in plenty of oxygen
  4. (D) A closed air hole
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Correct answer: (C) A saturated compound in plenty of oxygen

In plenty of air a saturated compound gives a clean flame.

51Board-style (practice)1 mark

Oxidation of ethanol gives —

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

Ethanol changes into ethanoic acid.

52Board-style (practice)1 mark

In sunlight CH4 + Cl2 gives —

  1. (A) CH3Cl and HCl
  2. (B) Only CO2
  3. (C) Only C and H2
  4. (D) Ethanol
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Correct answer: (A) CH3Cl and HCl

The products are chloromethane and HCl.

53Board-style (practice)1 mark

The temperature for dehydration of ethanol is —

  1. (A) 100 K
  2. (B) 290 K
  3. (C) 351 K
  4. (D) 443 K
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Correct answer: (D) 443 K

Ethene forms at 443 K.

54Board-style (practice)1 mark

Vinegar is —

  1. (A) Pure ethanol
  2. (B) 5–8% acetic acid
  3. (C) A soap solution
  4. (D) Hard water
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Correct answer: (B) 5–8% acetic acid

Vinegar is a 5–8% solution of acetic acid.

55Board-style (practice)1 mark

The white scum in hard water is formed by —

  1. (A) A detergent
  2. (B) Soap
  3. (C) Ethanol
  4. (D) Diamond
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Correct answer: (B) Soap

Soap forms scum. A detergent does not.

56BSEB model · practice (not an annual paper)1 mark

The saturated compound among these is —

  1. (A) C2H4
  2. (B) C2H2
  3. (C) C2H6
  4. (D) C3H6
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Correct answer: (C) C2H6

C2H6 is ethane and it is saturated.

57BSEB model · practice (not an annual paper)1 mark

Soap is —

  1. (A) A sodium salt of a long-chain acid
  2. (B) An alkane
  3. (C) Only an ester
  4. (D) A salt of hard water
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Correct answer: (A) A sodium salt of a long-chain acid

Soap is a sodium or potassium salt of a long-chain carboxylic acid.

58Competency-based (not a PYQ)1 mark

A student took oil and water in two tubes. Soap was added only to B, and both were shaken. In which tube does the oil layer separate first?

  1. (A) In A, where there is no soap
  2. (B) In B, where there is soap
  3. (C) In both at the same time
  4. (D) In neither
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Correct answer: (A) In A, where there is no soap

In tube A, without soap, the layers separate sooner.

59Competency-based (not a PYQ)1 mark

Four compounds are given: C2H6, C2H4, C2H2, CH4. Which ones undergo addition?

  1. (A) Only C2H6 and CH4
  2. (B) Only C2H4 and C2H2
  3. (C) All four
  4. (D) None
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Correct answer: (B) Only C2H4 and C2H2

Ethene and ethyne are unsaturated, so they add hydrogen.

← Chapter 4: Carbon and its Compounds — full notes, video, questions