Carbon

PYQ-Based MCQs (Q1–10)

The allotrope of carbon used in pencil is:
a) Diamond
b) Graphite
c) Charcoal
d) Coal
✅ b) Graphite
Explanation: Graphite is soft and slippery, hence used in pencil lead.
(BPSC 2019)
Diamond is an allotrope of:
a) Silicon
b) Carbon
c) Oxygen
d) Hydrogen
✅ b) Carbon
Explanation: Diamond and graphite are both crystalline forms of carbon.
(BPSC 2020)
Which form of carbon is used in dry cells?
a) Charcoal
b) Diamond
c) Graphite
d) Carbon black
✅ c) Graphite
Explanation: Graphite acts as the conductor (electrode) in dry cells.
(BPSC 66th Prelims)
Which is the hardest natural substance?
a) Quartz
b) Topaz
c) Diamond
d) Ruby
✅ c) Diamond
Explanation: Diamond is the hardest known natural material.
(BPSC 2018)
Which carbon allotrope conducts electricity?
a) Diamond
b) Graphite
c) Charcoal
d) Fullerene
✅ b) Graphite
Explanation: Due to free electrons, graphite can conduct electricity.
(BPSC Teacher 2023)
Which of the following is a carbon compound?
a) HCl
b) CH₄
c) NaCl
d) H₂O
✅ b) CH₄
Explanation: Methane is an organic compound of carbon and hydrogen.
(BPSC 64th)
Buckminsterfullerene is an allotrope of:
a) Oxygen
b) Carbon
c) Nitrogen
d) Sulphur
✅ b) Carbon
Explanation: C₆₀ is a spherical molecule of 60 carbon atoms.
(CDPO 2020)
The main element in organic compounds is:
a) Nitrogen
b) Oxygen
c) Carbon
d) Sulphur
✅ c) Carbon
Explanation: Organic chemistry is the chemistry of carbon compounds.
(BPSC 67th)
Which gas is produced when carbon burns in limited air?
a) CO₂
b) CO
c) CH₄
d) C₂H₆
✅ b) CO
Explanation: Incomplete combustion of carbon gives carbon monoxide.
(BPSC 2017)
Which compound is used in soft drinks as a gas?
a) Oxygen
b) Carbon monoxide
c) Carbon dioxide
d) Methane
✅ c) Carbon dioxide
Explanation: CO₂ creates fizz in sodas.
(BPSC 2015)

NCERT-Based MCQs (Q11–30)

Carbon belongs to which group in the periodic table?
a) Group 12
b) Group 14
c) Group 16
d) Group 2
✅ b) Group 14
Explanation: It has 4 valence electrons.
What is the valency of carbon?
a) 1
b) 2
c) 3
d) 4
✅ d) 4
Explanation: Carbon needs four electrons to complete its octet.
Which compound is known as marsh gas?
a) CO
b) CH₄
c) CO₂
d) H₂CO₃
✅ b) CH₄
Explanation: Methane is released from marshy places.
Which of the following shows catenation most effectively?
a) Carbon
b) Silicon
c) Oxygen
d) Sulphur
✅ a) Carbon
Explanation: Carbon forms strong C-C bonds, enabling long chains.
Which is not an allotrope of carbon?
a) Diamond
b) Graphite
c) CO₂
d) Fullerene
✅ c) CO₂
Explanation: CO₂ is a compound, not a form of elemental carbon.
Why diamond is hard and graphite is soft?
a) Different atomic number
b) Different bonding
c) One is compound
d) Due to impurities
✅ b) Different bonding
Explanation: Diamond has 3D covalent bonding; graphite has layers with weak forces.
What is the molecular formula of ethane?
a) C₂H₂
b) C₂H₄
c) C₂H₆
d) C₃H₈
✅ c) C₂H₆
Explanation: Ethane is a saturated hydrocarbon with two carbon atoms.
Which gas is formed on heating carbonates?
a) O₂
b) H₂
c) CO
d) CO₂
✅ d) CO₂
Explanation: Carbonates decompose to release CO₂ gas.
Which acid is formed when CO₂ dissolves in water?
a) HCl
b) H₂CO₃
c) HNO₃
d) CH₃COOH
✅ b) H₂CO₃
Explanation: CO₂ forms carbonic acid in water.
Which carbon allotrope has a tetrahedral structure?
a) Diamond
b) Graphite
c) Fullerene
d) Coal
✅ a) Diamond
Explanation: Each carbon is bonded to four others in a tetrahedral shape.
How many covalent bonds can carbon form?
a) 1
b) 2
c) 3
d) 4
✅ d) 4
Explanation: Carbon's tetravalency allows it to form four covalent bonds.
Which of the following is an unsaturated hydrocarbon?
a) Ethane
b) Propane
c) Ethene
d) Butane
✅ c) Ethene
Explanation: Ethene contains a double bond.
Carbon forms covalent bonds because:
a) It loses electrons easily
b) It gains electrons easily
c) It shares electrons
d) It has high melting point
✅ c) It shares electrons
Explanation: Carbon can't donate or accept 4 electrons easily, so it shares.
Which of these is a saturated hydrocarbon?
a) Ethene
b) Ethyne
c) Ethane
d) Benzene
✅ c) Ethane
Explanation: Alkanes are saturated hydrocarbons.
Which carbon allotrope is used in nanotechnology?
a) Graphite
b) Fullerene
c) Diamond
d) Charcoal
✅ b) Fullerene
Explanation: C₆₀ has unique properties for nanotech applications.
Graphite is soft because:
a) Layers slide easily
b) No bonding
c) Weak atoms
d) Small size
✅ a) Layers slide easily
Explanation: Weak van der Waals forces allow layers to slide.
Which carbon form is amorphous?
a) Diamond
b) Graphite
c) Charcoal
d) Fullerene
✅ c) Charcoal
Explanation: Charcoal has no crystalline structure.
Which hydrocarbon is used in LPG?
a) Ethane
b) Methane
c) Butane
d) Acetylene
✅ c) Butane
Explanation: LPG is mainly composed of butane and propane.
Which compound has triple bond?
a) Ethene
b) Ethyne
c) Methane
d) Propane
✅ b) Ethyne
Explanation: Ethyne has a triple bond between two carbon atoms.
Which gas contributes to acid rain?
a) CO
b) CO₂
c) SO₂
d) N₂
✅ c) SO₂
Explanation: SO₂ reacts with water to form sulphuric acid.

Predicted / Reference-Based MCQs (Q31–50)

Which of the following is the correct formula of methane?
a) C₂H₆
b) CH₄
c) C₂H₄
d) C₃H₈
✅ b) CH₄
Explanation: Methane is the simplest alkane with one carbon and four hydrogen atoms.
Which property of carbon allows it to form a large number of compounds?
a) Radioactivity
b) Catenation
c) Ion formation
d) Isomerism
✅ b) Catenation
Explanation: Catenation is the ability of carbon to form long chains and rings with itself.
Which functional group is present in aldehydes?
a) –OH
b) –CHO
c) –COOH
d) –CO–
✅ b) –CHO
Explanation: The –CHO group defines aldehydes, e.g., formaldehyde (HCHO).
Which of the following compounds is a ketone?
a) CH₃COOH
b) CH₃OH
c) CH₃COCH₃
d) CH₃CH₂OH
✅ c) CH₃COCH₃
Explanation: Acetone (propanone) is a ketone with a –CO– group between carbon atoms.
Which of the following is a hydrocarbon?
a) Ethanol
b) Acetone
c) Methane
d) Acetic acid
✅ c) Methane
Explanation: Hydrocarbons are compounds made of only hydrogen and carbon atoms.
Which organic compound is responsible for rancidity in food?
a) Alkanes
b) Esters
c) Aldehydes
d) Unsaturated fatty acids
✅ d) Unsaturated fatty acids
Explanation: They react with oxygen to produce unpleasant odors and tastes.
The formula C₂H₂ belongs to which group?
a) Alkane
b) Alkene
c) Alkyne
d) Alcohol
✅ c) Alkyne
Explanation: Ethyne (C₂H₂) is the first member of alkynes with a triple bond.
Which type of compound is formed during saponification?
a) Alcohol
b) Acid
c) Soap
d) Ketone
✅ c) Soap
Explanation: Saponification is the reaction of fat with base to produce soap.
Which of these compounds can undergo addition reaction?
a) Ethane
b) Ethene
c) Propane
d) Butane
✅ b) Ethene
Explanation: Ethene is unsaturated and undergoes addition reactions like bromination.
Which of the following is used to test for the presence of double bonds in a compound?
a) Iodine
b) Bromine water
c) Copper sulfate
d) Lime water
✅ b) Bromine water
Explanation: Unsaturated compounds decolorize bromine water.
Combustion of carbon in excess oxygen forms:
a) CO
b) CO₂
c) H₂O
d) C₂H₂
✅ b) CO₂
Explanation: Complete combustion of carbon yields carbon dioxide.
Combustion of carbon in limited oxygen forms:
a) CO₂
b) CO
c) C₂H₄
d) CH₄
✅ b) CO
Explanation: Incomplete combustion forms carbon monoxide, a toxic gas.
Fullerenes are:
a) Alloys
b) Compounds of carbon and metal
c) Hollow spheres of carbon
d) Acids
✅ c) Hollow spheres of carbon
Explanation: Buckminsterfullerene (C₆₀) is a spherical molecule of carbon atoms.
Organic compounds always contain:
a) Oxygen
b) Nitrogen
c) Carbon
d) Sulfur
✅ c) Carbon
Explanation: Carbon is the essential element in all organic compounds.
Which gas is produced when acetic acid reacts with sodium carbonate?
a) H₂
b) CO₂
c) CH₄
d) NH₃
✅ b) CO₂
Explanation: The acid-carbonate reaction releases carbon dioxide gas.
Which of the following is used in the preparation of soap?
a) Sodium hydroxide
b) Potassium nitrate
c) Calcium carbonate
d) Nitric acid
✅ a) Sodium hydroxide
Explanation: NaOH reacts with oils/fats to produce soap.
What kind of bond exists between carbon atoms in ethene?
a) Single bond
b) Double bond
c) Triple bond
d) Ionic bond
✅ b) Double bond
Explanation: Ethene (C₂H₄) has a double bond between carbon atoms.
What is the IUPAC name of formaldehyde?
a) Methanal
b) Methanol
c) Formic acid
d) Methanoic acid
✅ a) Methanal
Explanation: Formaldehyde (HCHO) is the simplest aldehyde.
Which compound is formed when ethanol is oxidized?
a) Methanol
b) Acetic acid
c) Ethanoic acid
d) Both b and c
✅ d) Both b and c
Explanation: Acetic acid is the common name; Ethanoic acid is the IUPAC name.
What is the general formula for alkanes?
a) CnH₂n
b) CnH₂n+2
c) CnH₂n–2
d) CnHn
✅ b) CnH₂n+2
Explanation: Alkanes are saturated hydrocarbons following this formula.