Class XI Chemistry*
Multiple Choice Questions (Each question carries 1 mark)
1. The IUPAC name of (CH₃)₂CHCH₂CH(CH₃)₂ is:
A) 2,4-Dimethylpentane B) 3,3-Dimethylpentane
C) 2,3-Dimethylpentane D) 3,4-Dimethylpentane
2.The correct IUPAC name of the compound CH₃CH=C(CH₃)₂ is:
A) 2-Methyl-2-butene B) 3-Methyl-2-butene
C) 2,2-Dimethylpropene D) Isobutene
3. The IUPAC name of the compound (CH₃)₂C=CHCH₃ is:
A) 2-Methyl-2-butene B) 3-Methyl-1-butene
C) 2,3-Dimethylbutene D) 3-Methyl-2-butene
4. The IUPAC name of CH₃CH₂C(CH₃)₂CH₂CH₃ is:
A) 3,3-Dimethylpentane B) 2,2-Dimethylpentane
C) 2,3-Dimethylpentane D) 3,4-Dimethylpentane
5.The IUPAC name of (CH₃)₃CCH₂CH₂OH is:
A) 3,3-Dimethylpropan-1-ol B) 2,2-Dimethylpropan-1-ol
C) 3,3-Dimethylbutan-1-ol D) 2,2-Dimethylbutan-1-ol
6. The IUPAC name of CH₃CH(CH₃)CH₂COCH₃ is:
A) 4-Methyl-2-pentanone B) 3-Methyl-2-pentanone
C) 2-Methyl-3-pentanone D) 4-Methyl-3-pentanone
7. The correct IUPAC name for (CH₃)₃CCH₂COOH is:
A) 3,3-Dimethylbutanoic acid B) 2,2-Dimethylbutanoic acid
C) 3,3-Dimethylpentanoic acid D) 2,2-Dimethylpentanoic acid
8.The IUPAC name of the compound with structure CH₃COCH₂CH₂CHO is:
A) 4-Oxopentanal B) 5-Oxopentanal C) 2-Oxopentanal D) 3-Oxopentanal
9. The IUPAC name of (CH₃)₂CHCH=CHCHO is:
A) 4-Methylpent-2-enal B) 3-Methylpent-2-enal
C) 3-Methylpent-3-enal D) 2-Methylpent-2-enal
10.The IUPAC name of CH₃CH(OH)CH(CH₃)₂ is:
A) 3-Methyl-2-butanol B) 2-Methyl-2-butanol
C) 2-Methyl-3-butanol D) 3-Methyl-3-butanol
11. The IUPAC name of CH₃CH(Br)CH₂CH₃ is:
A) 2-Bromobutane B) 3-Bromobutane C) 1-Bromobutane D) tert-Butyl bromide
12.The IUPAC name of (CH₃CH₂)₂O is:
A) Ethoxyethane B) Diethyl ether C) Ethoxy methane D) Dimethyl ether
13.The correct IUPAC name for CH₃CH=C(CH₃)CH₂CH₃ is:
A) 3-Methylpent-2-ene B) 4-Methylpent-2-ene
C) 2-Methylpent-2-ene D) 3-Methylpent-1-ene
14.The IUPAC name of CH₃CH₂CH=CHCN is:
A) Pent-3-enenitrile B) Pent-2-enenitrile C) But-2-enenitrile D) But-3-enenitrile
15.The correct IUPAC name of (CH₃)₂CHCH₂CH₂COOH is:
A) 3-Methylpentanoic acid B) 2-Methylhexanoic acid
C) 4-Methylhexanoic acid D) 2-Methylpentanoic acid
16.The IUPAC name of (CH₃CH₂)₃CBr is:
A) tert-Butyl bromide B) 1-Bromo-3-methylbutane
C) 1-Bromo-2,2-dimethylpropane D) 2-Bromo-2,3-dimethylbutane
17.The IUPAC name of CH₃CH=C(CH₃)CH₂CH₂CH₃ is:
A) 3-Methylhex-2-ene B) 2-Methylhex-2-ene
C) 3-Methylhex-1-ene D) 2-Methylhex-3-ene
18.The compound CH₃CH=C(CH₃)CH=CH₂ is named as:
A) 2,4-Dimethyl-1,3-pentadiene B) 2-Methyl-1,3-pentadiene
C) 3-Methyl-1,4-pentadiene D) 2,3-Dimethyl-1,4-pentadiene
19.The IUPAC name of C₆H₅CH=CHCOOH is:
A) 3-Phenylpropanoic acid B) Cinnamic acid
C) 2-Phenylethanoic acid D) 2-Phenylpropanoic acid
20.The IUPAC name of (CH₃)₃CCH₂COCH₃ is:
A) 3,3-Dimethyl-2-butanone B) 4,4-Dimethyl-2-pentanone
C) 3,3-Dimethyl-2-pentanone D) 4,4-Dimethyl-3-pentanone
Multiple Choice Questions (Each question carries 1 mark)
1. The IUPAC name of C₆H₅CH₃ is:
A) Phenylmethane B) Methylbenzene C) Toluene D) Benzylmethane
2. The IUPAC name of o-dichlorobenzene is:
A) 1,2-Dichlorobenzene B) 1,3-Dichlorobenzene
C) 1,4-Dichlorobenzene D) Benzene dichloride
3. The compound C₆H₅NO₂ is named as:
A) Phenyl nitrite B) Nitrobenzene C) Aminobenzene D) Benzenamine
4. The IUPAC name of benzene with an –OH group is:
A) Benzyl alcohol B) Phenol C) Hydroxybenzene D) Benzenol
5. The IUPAC name of C₆H₅NH₂ is:
A) Aniline B) Aminobenzene C) Benzenamine D) All of the above
6. The IUPAC name of CH₃C₆H₄NO₂ (p-isomer) is:
A) 4-Nitrotoluene B) 2-Nitrotoluene C) 3-Nitrotoluene D) p-Methyl nitrobenzene
7. The IUPAC name of CH₃C₆H₄OH (o-isomer) is:
A) 1-Methyl-2-hydroxybenzene B) 2-Methylphenol C) o-Cresol D) All of these
8. The compound C₆H₅COOH is called:
A) Phenol B) Benzoic acid C) Benzaldehyde D) Benzyl alcohol
9. The IUPAC name of C₆H₅CHO is:
A) Benzene carboxaldehyde B) Benzaldehyde C) Phenylmethanal D) Both B and C
10. The IUPAC name of C₆H₅CH₂OH is:
A) Benzyl alcohol B) Phenylmethanol C) Both A and B D) Phenol
11. The compound with formula (CH₃)₂CHC₆H₅ is:
A) Isopropylbenzene B) Cumene C) 2-Phenylpropane D) All of the above
12.The IUPAC name of CH₃C₆H₄CHO (p-isomer) is:
A) 4-Methylbenzaldehyde B) 2-Methylbenzaldehyde
C) 3-Methylbenzaldehyde D) p-Methylbenzaldehyde
13.The IUPAC name of the compound CH₃C₆H₄COOH (m-isomer) is:
A) 3-Methylbenzoic acid B) 4-Methylbenzoic acid
C) 2-Methylbenzoic acid D) m-Methylbenzoic acid
14.The IUPAC name of C₆H₅CH₂NH₂ is:
A) Benzylamine B) Phenylmethylamine C) Both A and B D) Benzenamine
15.The compound C₆H₅OCH₃ is known as:
A) Methoxybenzene B) Phenyl methyl ether C) Anisole D) All of these
16. The IUPAC name of NO₂C₆H₄COOH (p-isomer) is:
A) 4-Nitrobenzoic acid B) 2-Nitrobenzoic acid
C) 3-Nitrobenzoic acid D) p-Nitrobenzoic acid
Isomerism
1. What is the definition of isomerism?
A) Different compounds with the same molecular formula but different arrangements of atoms
B) Compounds with different molecular formulas but similar structures
C) Compounds that have the same physical properties
D) Different elements combined in a compound
2. Which of the following is NOT a type of isomerism?
A) Structural isomerism
B) Geometric isomerism
C) Optical isomerism
D) Ionic isomerism
3. Which type of isomerism arises due to different arrangements of atoms in space around a double bond?
A) Structural isomerism
B) Geometric isomerism
C) Optical isomerism
D) Functional isomerism
4. In optical isomerism, isomers are also called:
A) Enantiomers
B) Diastereomers
C) Conformers
D) Tautomers
5. Which of the following compounds can exhibit geometric isomerism?
A) Ethane (C2H6)
B) Ethene (C2H4)
C) Methane (CH4)
D) Propane (C3H8)
6. Which of the following is an example of functional isomerism?
A) Butane and isobutane
B) Ethanol and dimethyl ether
C) Cis-butene and trans-butene
D) Lactic acid and alanine
7. The phenomenon where compounds have the same formula but differ in the connectivity of atoms is called:
A) Optical isomerism
B) Structural isomerism
C) Geometric isomerism
D) Conformational isomerism
8. Which statement is true about cis-trans isomers?
A) They have different molecular formulas
B) They have the same physical and chemical properties
C) They differ in the spatial arrangement of groups around a double bond or ring
D) They cannot be separated
9. Chirality in molecules is associated with:
A) A plane of symmetry
B) A carbon atom bonded to four different groups
C) A double bond in the molecule
D) Identical groups attached to the carbon atom
10. Which of the following is NOT a property that can differ between isomers?
A) Boiling point
B) Melting point
C) Molecular weight
D) Optical activity
Answer key
- A) Different compounds with the same molecular formula but different arrangements of atoms
- D) Ionic isomerism
- B) Geometric isomerism
- A) Enantiomers
- B) Ethene (C2H4)
- B) Ethanol and dimethyl ether
- B) Structural isomerism
- C) They differ in the spatial arrangement of groups around a double
- B) A carbon atom bonded to four different groups
- C) Molecular weight
Isomerism 2
1. Explain the difference between structural isomerism and stereoisomerism with suitable examples.
2. Draw all possible chain isomers of pentane and name them.
3. What is positional isomerism? Illustrate with an example involving pentene.
4. Define functional isomerism and give two examples of functional isomers with molecular formula C3H6O.
5. Explain tautomerism with the keto-enol tautomerism of acetaldehyde.
6. What is geometrical (cis-trans) isomerism? Draw the cis and trans isomers of 1,2-dichloroethene.
7. Explain why cis-isomers generally have higher boiling points than trans-isomers.
8. Define optical isomerism and explain the role of a chiral center with an example.
9. How many stereoisomers are possible for 2,3-dibromobutane? Explain.
10. Differentiate between enantiomers and diastereomers with examples.
12. What is racemic mixture? How can it be resolved into individual enantiomers?
14. Discuss the concept of conformational isomerism with reference to ethane.
15.How does the presence of double bonds affect the possibility of rotation and isomerism?
17. Write the number of isomers of C4H8 and classify them.
Chapter GOC
1. 1
Answer (structural/formula form):
HO–CH₂–CH₂–CH₂–CH(CH₃)–CH(CH₃)–COOH
- IUPAC name of the compound
shown (CH₃–CH(–NO₂)–C(=O)–CH(–CH₃)–CH₃)
Answer: 2-Nitro-4-methylpentan-3-one
- The central atom of
CH₂=C=CH₂ is ______ hybridized.
Answer: sp - Assertion: Carbocations are
planar in nature.
Reason: Carbocations are sp² hybridized.
Answer: (a) Both A and R are correct and Reason is the correct explanation.
(Planarity follows from the empty p orbital and sp² hybridization of the positively charged carbon.)
- Assertion: All the carbon
atoms of But-2-ene lie in a plane.
Reason: All the carbon atoms in But-2-ene are sp² hybridized.
Answer: (c) Both Assertion and Reason are incorrect.
(But-2-ene has two internal sp² carbons that are planar, but the terminal methyl carbons are sp³ — so not all carbons are sp² nor are all carbons in one plane.)
- (i) What type of isomerism
is exhibited by the pair CH₃CH₂CHO and CH₃COCH₃?
Answer: Functional-group isomerism (aldehyde vs. ketone).
(ii) Give
one example each of a nucleophile and an electrophile.
Answer: Nucleophile: OH⁻ (or :NH₃, :CN⁻) — electron pair donor.
Electrophile: H⁺ (or NO₂⁺, R⁺ carbocation) — electron pair acceptor.
Unit Test I — Answers
(Questions 1–5)
1. Answer
: (d)
BF₃ — boron trifluoride is electron-deficient (Lewis acid) and accepts
electron pairs, so it acts as an electrophile.
2. Answer: (b) C₆H₅CH·CH₃ — the
benzylic secondary radical (adjacent to the aromatic ring) is
resonance-stabilized and is more stable than simple alkyl radicals.
3.Hyperconjugation (also called σ-conjugation or
Baker–Nathan effect). No-bond resonance refers to delocalization involving σ
(C–H or C–C) bonds.
4. Assertion: In CH₂ = C = CH₂ all
the carbon atoms are sp² hybridized.
Reason : All the hydrogen atoms lie in one plane.
Answer: (c) Both Assertion and
Reason are incorrect.
(Explanation: In allene the central carbon is sp hybridized and the
terminal carbons are sp²; the terminal CH₂ groups lie in perpendicular
planes, so H atoms are not all in one plane.)
5. Assertion: Glycerol is purified
by distillation under reduced pressure.
Reason : Organic compound in liquid state are purified by distillation.
Answer: (b) Both Assertion and
Reason are correct but Reason is not the correct explanation.
(Explanation: Glycerol is purified by vacuum distillation because it has a high
boiling point and would decompose on normal distillation; the Reason is a true
general statement but does not explain why reduced pressure is needed.)
6. Give IUPAC name of the following compounds :
(a) C₆H₅CH₂CH₂OH
Answer: 2‑Phenylethanol (common name:
phenethyl alcohol).
(b) Structure: CH₃–CH(Br)–C(=O)–CH(CH₃)–CH₃
Answer: 2‑Bromo‑4‑methylpentan‑3‑one
(Parent chain = pentan‑3‑one; substituents at C‑2 = bromo, C‑4 = methyl.)
7. Discuss the principle of steam distillation.
Steam distillation separates volatile, water‑immiscible (or partially
immiscible) organic compounds at temperatures below their boiling points. When
steam is passed through (or the compound is co‑distilled with water), the total
vapour pressure of the system is the sum of vapour pressures of water and the
organic compound; the mixture boils when this sum equals atmospheric pressure,
allowing distillation at a lower temperature and preventing thermal
decomposition.
8. Explain the reason for the fusion of an organic compound with
metallic sodium for testing nitrogen, sulphur and halogens.
Fusion with sodium (Lassaigne’s test) converts covalently bound heteroatoms
into their corresponding ionic forms (e.g., nitrogen → NaCN/NaCN-derived
species, sulphur → Na₂S, halogens → NaX). These inorganic salts are water‑soluble
and can be extracted into water and subsequently detected with specific
reagents (FeSO₄/HCl for N, lead acetate or sodium nitroprusside for S, silver
nitrate for halides).
9. What are the various conditions essential for resonance?
1. Presence
of conjugated π bonds or lone pairs adjacent to π bonds (alternate
single and multiple bonds or lone pair–π adjacency).
2. Planarity
of the system so p orbitals can overlap effectively.
3. Continuous
overlap of parallel p orbitals (a cyclic or linear array of p
orbitals) to allow delocalization of electrons.
(Any three clear points explaining these ideas earn full credit.)
10. Suggest a method to separate the constituents from the following
mixtures :
(a) Mixture of two miscible liquids.
Use fractional distillation (fractionating column). Heat the
mixture and collect fractions at different boiling ranges; components separate
based on differing boiling points.
(b) A mixture of oil and water.
Use a separatory funnel (liquid–liquid extraction/decantation)
to separate the immiscible layers; the denser layer is drained off first. For
finer separation, wash with solvents or use centrifugation.
(c) A mixture of plant pigments.
Use chromatography — e.g., column chromatography
or paper/TLC to separate pigments based on polarity and
adsorption. Often pigments are first extracted with an appropriate solvent
(acetone/ethanol) and then separated on a chromatographic medium.
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