CUET UG Chemistry Booster Test -2 Introduction and Basic Concepts -

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CUET UG Chemistry Booster Test -2 Introduction and Basic Concepts

⏱️ 30 Minutes

❓ 20 Questions

📌 Answers are locked once submitted — results and explanations appear at the end.

CUET UG Chemistry Booster Test -2 Introduction and Basic Concepts

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QUESTION 1 OF 20

The IUPAC name of the secondary haloalkane CH₃CH₂CH(Br)CH₃ is:

Answer Review

1 The IUPAC name of the secondary haloalkane CH₃CH₂CH(Br)CH₃ is:

A 2-Bromobutane

B 1-Bromobutane

C 2-Bromopentane

D 3-Bromobutane

💡 Short Explanation

The parent chain contains 4 carbon atoms (butane). Bromine is attached to the second carbon. Therefore, the IUPAC name is 2-Bromobutane.

✅ Correct Answer Explanation

The structure CH₃CH₂CH(Br)CH₃ contains a continuous chain of four carbon atoms. Numbering from the end nearest the bromine atom: CH₃–CH(Br)–CH₂–CH₃ The bromine substituent is located on carbon-2. Hence, the correct IUPAC name is 2-Bromobutane.

❓ Why Other Options Are Incorrect

B. 1-Bromobutane
Bromine is not attached to carbon-1.
C. 2-Bromopentane
Contains five carbons, not four.
D. 3-Bromobutane
Violates the lowest locant rule.

🎯 Strategy

Used

IUPAC Nomenclature

🧠 Memory Trick

Butane + Br on Carbon-2 = 2-Bromobutane

📚 Class XII Chemistry – Haloalkanes and Haloarenes – Nomenclature

2 Which of the following structures definitively contains a halogen atom directly bonded to an sp²-hybridised carbon of an aromatic ring?

A Benzyl chloride

B Chlorobenzene

C Allyl bromide

D Vinyl chloride

💡 Short Explanation

In chlorobenzene, chlorine is directly attached to a benzene ring carbon. Benzene ring carbons are sp² hybridised. Therefore, chlorobenzene is a haloarene.

✅ Correct Answer Explanation

In chlorobenzene (C₆H₅Cl), the chlorine atom is directly bonded to a carbon atom of the benzene ring. Since benzene ring carbons are sp² hybridised, chlorobenzene is a classic example of a haloarene.

❓ Why Other Options Are Incorrect

A. Benzyl chloride
Chlorine is attached to a benzylic CH₂ carbon (sp³).
C. Allyl bromide
Bromine is attached to an allylic sp³ carbon.
D. Vinyl chloride
Halogen is attached to an sp² carbon, but not an aromatic ring.

🎯 Strategy

Used

Structure Identification

🧠 Memory Trick

Haloarene = Halogen directly on benzene ring

📚 Class XII Chemistry – Haloalkanes and Haloarenes – Classification

3 The deficiency of the natural iodine-containing hormone thyroxine directly leads to which clinical condition?

A Malaria

B Typhoid

C Goiter

D Scurvy

💡 Short Explanation

Thyroxine contains iodine. Iodine deficiency reduces thyroxine production. This leads to enlargement of the thyroid gland (goiter).

✅ Correct Answer Explanation

Thyroxine is an iodine-containing hormone produced by the thyroid gland. When iodine intake is insufficient: Thyroxine synthesis decreases. Thyroid gland enlarges in an attempt to compensate. The resulting condition is called goiter.

❓ Why Other Options Are Incorrect

A. Malaria
Caused by Plasmodium infection.
B. Typhoid
Caused by Salmonella typhi.
D. Scurvy
Caused by vitamin C deficiency.

🎯 Strategy

Used

Application of Biological Importance

🧠 Memory Trick

Iodine ↓ → Thyroxine ↓ → Goiter

📚 Class XII Chemistry – Haloalkanes and Haloarenes – Naturally Occurring Organohalogen Compounds

4 Match the Following

List 1 (Synthetic Compound)	List 2 (Historical/Current Use)
1. Chloroform	a. Production of Freon R-22
2. Halothane	b. Anaesthetic during surgery
3. Freon-12	c. Aerosol propellants and refrigeration
4. Carbon tetrachloride	d. Spot remover and fire extinguisher

A 1-a, 2-b, 3-c, 4-d

B 1-b, 2-a, 3-d, 4-c

C 1-d, 2-c, 3-b, 4-a

D 1-c, 2-d, 3-a, 4-b

💡 Short Explanation

Chloroform → Freon R-22 production. Halothane → Anaesthetic. Freon-12 → Refrigeration and aerosols. Carbon tetrachloride → Cleaning and fire extinguishers.

✅ Correct Answer Explanation

Synthetic Compound — Use Chloroform — Production of Freon R-22 Halothane — Anaesthetic during surgery Freon-12 — Refrigerants and aerosol propellants Carbon tetrachloride — Spot remover and fire extinguisher Therefore: 1-a, 2-b, 3-c, 4-d

❓ Why Other Options Are Incorrect

Options B, C and D contain incorrect pairings of compounds and their applications.

🎯 Strategy

Used

Concept Association

🧠 Memory Trick

Chloroform → Freon, Halothane → Hospital

📚 Class XII Chemistry – Haloalkanes and Haloarenes – Polyhalogen Compounds

5 Industrial characteristics of polyhalogen compounds:
(A) Dichloromethane exposure can mildly impair hearing and vision.
(B) Chloroform reacts with air and light to form poisonous phosgene.
(C) Freon production utilizes CCl₄ as feedstock.
(D) Iodoform is currently used heavily in medicine due to its pleasant smell.

A A, B, C

B B, C, D

C A, C, D

D A, B, D

💡 Short Explanation

Statements A, B and C are correct. Iodoform is not heavily used in medicine today.

✅ Correct Answer Explanation

A. Correct Dichloromethane exposure may affect hearing and vision. B. Correct Chloroform forms toxic phosgene (COCl₂) in air and sunlight. C. Correct Carbon tetrachloride is used in Freon manufacture. D. Incorrect Iodoform has limited antiseptic use and is not widely used today.

❓ Why Other Options Are Incorrect

Any option containing statement D is incorrect because D is false.

🎯 Strategy

Used

Statement Verification

🧠 Memory Trick

Dichloromethane–Chloroform–Freon = Important Industrial Trio

📚 Class XII Chemistry – Haloalkanes and Haloarenes – Polyhalogen Compounds

6 Why are fully fluorinated compounds being heavily investigated in the medical surgical field?

A They act as fast-acting general anaesthetics

B They show potential as blood substitutes

C They are highly effective at curing malaria

D They destroy antibiotic-resistant microorganisms

💡 Short Explanation

Fully fluorinated compounds can dissolve large amounts of oxygen. They are being explored as artificial blood substitutes. Useful in surgery and emergency medicine.

✅ Correct Answer Explanation

Certain fully fluorinated compounds possess exceptional oxygen-carrying capacity. Because of this property, researchers are investigating them as: Artificial blood substitutes Oxygen transport media Emergency transfusion alternatives

❓ Why Other Options Are Incorrect

A.
Not their primary medical application.
C.
Not antimalarial drugs.
D.
Not used as antibiotics.

🎯 Strategy

Used

Application-Based Recall

🧠 Memory Trick

Fluorinated Compounds → Future Blood

📚 Class XII Chemistry – Haloalkanes and Haloarenes – Applications

7 Why did significant ecological problems related to the extensive use of DDT begin to appear in the late 1940s?

A It evaporated too quickly into the atmosphere

B It is highly fat-soluble and not rapidly metabolised, causing bioaccumulation

C It degrades immediately in soil leaving toxic metals

D It rapidly reacts with stratospheric ozone

💡 Short Explanation

DDT is highly stable. It accumulates in fatty tissues. Bioaccumulation causes ecological damage.

✅ Correct Answer Explanation

DDT is: Fat soluble Chemically stable Poorly metabolised As a result, it accumulates in organisms and moves through food chains, producing serious ecological consequences.

❓ Why Other Options Are Incorrect

A, C and D do not describe the primary reason for DDT-related ecological problems.

🎯 Strategy

Used

Environmental Application

🧠 Memory Trick

DDT = Doesn't Decompose Timely

📚 Class XII Chemistry – Haloalkanes and Haloarenes – Environmental Effects

8 When carbon tetrachloride is released into the air, it slowly rises to the upper atmosphere causing which major environmental hazard?

A Acid rain

B Depletion of the ozone layer

C Eutrophication

D Photochemical smog

💡 Short Explanation

Carbon tetrachloride reaches the stratosphere. It contributes to ozone destruction. This increases UV radiation exposure.

✅ Correct Answer Explanation

Carbon tetrachloride is highly stable and can persist long enough to reach the stratosphere. There it participates in reactions that: Destroy ozone molecules Thin the ozone layer Increase harmful UV radiation reaching Earth

❓ Why Other Options Are Incorrect

A, C and D are unrelated to the major effect described in NCERT.

🎯 Strategy

Used

Environmental Impact Analysis

🧠 Memory Trick

CCl₄ → Climbs → Ozone Damage

📚 Class XII Chemistry – Haloalkanes and Haloarenes – Environmental Effects

9 Most haloalkanes display considerably higher boiling points than their parent hydrocarbons of comparable molecular mass predominantly because:

A They have remarkably weaker van der Waals forces

B They form strong intermolecular hydrogen bonds

C They possess greater molecular polarity and higher molecular mass

D They are completely non-polar solids

💡 Short Explanation

Haloalkanes are more polar. They generally have higher molecular masses. Stronger intermolecular attractions increase boiling point.

✅ Correct Answer Explanation

Compared to hydrocarbons: Haloalkanes contain polar C–X bonds. They have greater molecular mass. Stronger dipole-dipole and van der Waals forces exist. Hence, their boiling points are higher.

❓ Why Other Options Are Incorrect

A. Opposite of the truth.
B. Haloalkanes generally do not form hydrogen bonds.
D. Haloalkanes are not completely non-polar solids.

🎯 Strategy

Used

Property Correlation

🧠 Memory Trick

More Mass + More Polarity = Higher Boiling Point

📚 Class XII Chemistry – Haloalkanes and Haloarenes – Physical Properties

10 Which statement precisely explains why DDT use is environmentally detrimental in terms of its chemical stability?

A It decomposes rapidly in sunlight creating smog

B It is highly soluble in water and poisons aquifers

C Its high chemical stability and fat solubility lead to storage in animal fatty tissues

D It acts as a highly reactive electrophile in soil

💡 Short Explanation

DDT is persistent and fat soluble. It accumulates in organisms. This leads to biomagnification.

✅ Correct Answer Explanation

DDT is chemically stable and lipid soluble. Therefore: It is not rapidly degraded. It accumulates in fatty tissues. Its concentration increases along food chains. This phenomenon is known as bioaccumulation and biomagnification.

❓ Why Other Options Are Incorrect

A. DDT does not rapidly decompose.
B. Water solubility is low.
D. Not the primary environmental concern.

🎯 Strategy

Used

Environmental Reasoning

🧠 Memory Trick

DDT = Dissolves in Fat, Stays for Years

📚 Class XII Chemistry – Haloalkanes and Haloarenes – Environmental Effects

11 Based on the passage, why is the carbon-halogen bond highly polarised?

A Carbon atoms are larger than halogen atoms

B Halogen atoms are more electronegative than carbon

C The bond is purely ionic in nature

D Halogen atoms release electrons to the carbon

💡 Short Explanation

Halogens are more electronegative than carbon. They attract the bonding electron pair toward themselves. This creates a polar C–X bond.

✅ Correct Answer Explanation

In haloalkanes and haloarenes, the carbon-halogen bond is polar because halogen atoms (F, Cl, Br, I) are more electronegative than carbon. As a result: Electron density shifts toward the halogen atom. Halogen acquires a partial negative charge (δ⁻). Carbon acquires a partial positive charge (δ⁺). This unequal sharing of electrons causes polarization of the C–X bond.

❓ Why Other Options Are Incorrect

A. Carbon atoms are larger than halogen atoms
Size difference is not the reason for bond polarity.
C. The bond is purely ionic in nature
The C–X bond is covalent but polar.
D. Halogen atoms release electrons to the carbon
Halogens attract electrons, not donate them.

🎯 Strategy

Used

Electronegativity Concept

🧠 Memory Trick

Halogen = Electron Puller → Polar Bond

📚 Class XII Chemistry – Haloalkanes and Haloarenes – Nature of C–X Bond

12 According to the passage, as the size of the halogen atom increases from fluorine to iodine, what inevitably happens to the C–X bond length?

A It decreases significantly

B It increases

C It remains constant

D It fluctuates randomly

💡 Short Explanation

Atomic size increases from F to I. Larger halogens form longer C–X bonds. Bond length order: C–F < C–Cl < C–Br < C–I.

✅ Correct Answer Explanation

As we move down Group 17: F < Cl < Br < I The atomic radius increases progressively. Therefore, the distance between carbon and the halogen atom also increases: C–F < C–Cl < C–Br < C–I Hence, bond length increases from fluorine to iodine.

❓ Why Other Options Are Incorrect

A.
Opposite trend.
C.
Bond lengths are not identical.
D.
The trend is systematic, not random.

🎯 Strategy

Used

Periodic Trend Analysis

🧠 Memory Trick

Bigger Halogen = Bigger Bond Length

📚 Class XII Chemistry – Haloalkanes and Haloarenes – C–X Bond Characteristics

13 Arrange the following sp³ bonded primary alkyl halides in decreasing order of their boiling points for a given alkyl group (R):
(A) R–Cl
(B) R–I
(C) R–Br
(D) R–F

A (B), (C), (A), (D)

B (A), (B), (C), (D)

C (D), (A), (C), (B)

D (B), (A), (D), (C)

💡 Short Explanation

Boiling point increases with molecular mass. Iodides have the highest molar mass. Fluorides have the lowest.

✅ Correct Answer Explanation

For the same alkyl group: R–F < R–Cl < R–Br < R–I As the size and molar mass of the halogen increase: Van der Waals forces become stronger. Boiling points increase. Therefore, decreasing order of boiling points is: R–I > R–Br > R–Cl > R–F or (B) > (C) > (A) > (D)

❓ Why Other Options Are Incorrect

Options B, C and D do not follow the trend of increasing molecular mass and intermolecular attraction.

🎯 Strategy

Used

Physical Property Correlation

🧠 Memory Trick

I > Br > Cl > F (Boiling Point Order)

📚 Class XII Chemistry – Haloalkanes and Haloarenes – Physical Properties

14 Identify the reaction type where a mixture of an sp² hybridised aryl halide and an sp³ hybridised alkyl halide gives an alkylarene upon treatment with sodium in dry ether.

A Fittig

B Wurtz-Fittig

C Wurtz

D Sandmeyer

💡 Short Explanation

Aryl halide + Alkyl halide + Na/dry ether. Produces an alkylarene. This reaction is called Wurtz-Fittig reaction.

✅ Correct Answer Explanation

The Wurtz-Fittig reaction involves: Aryl halide + Alkyl halide + Sodium + Dry ether Result: [Ar-X + R-X {2Na} Ar-R] An alkylarene is formed.

❓ Why Other Options Are Incorrect

A. Fittig
Uses two aryl halides.
C. Wurtz
Uses two alkyl halides.
D. Sandmeyer
Involves diazonium salts.

🎯 Strategy

Used

Named Reaction Identification

🧠 Memory Trick

Wurtz + Fittig = Alkyl + Aryl

📚 Class XII Chemistry – Haloalkanes and Haloarenes – Wurtz and Fittig Reactions

15 Alkyl halides play a crucial synthetic role and can be converted into alkyl cyanides by reacting with which reagent?

A AgCN

B KCN

C KNO₂

D AgNO₂

💡 Short Explanation

KCN provides free CN⁻ ions. CN⁻ attacks through carbon. Alkyl cyanides (nitriles) are formed.

✅ Correct Answer Explanation

When alkyl halides react with potassium cyanide (KCN): [ R-X + KCN R-CN + KX ] The cyanide ion attacks through its carbon atom, producing an alkyl cyanide (nitrile). This reaction is important because it increases the carbon chain length by one carbon atom.

❓ Why Other Options Are Incorrect

A. AgCN
Mainly forms isocyanides (R–NC).
C. KNO₂
Produces alkyl nitrites (R–ONO).
D. AgNO₂
Produces nitroalkanes (R–NO₂).

🎯 Strategy

Used

Reagent–Product Correlation

🧠 Memory Trick

KCN → Cyanide → R–CN (Nitrile)

📚 Class XII Chemistry – Haloalkanes and Haloarenes – Nucleophilic Substitution Reactions

16 The unit of density for liquid haloalkane solvents is standardly expressed as:

A g/mL

B V

C S cm⁻¹

D Debye

💡 Short Explanation

Density is mass per unit volume. Liquid densities are commonly expressed in g/mL. Haloalkane solvents are liquids under ordinary conditions.

✅ Correct Answer Explanation

Density is defined as: [ Density} = Mass/Volume ] For liquids such as haloalkanes, the standard laboratory unit is grams per millilitre (g/mL). Examples: Water = 1.0 g/mL Carbon tetrachloride ≈ 1.6 g/mL Hence, g/mL is the appropriate unit for expressing the density of liquid haloalkane solvents.

❓ Why Other Options Are Incorrect

B. V
Unit of electric potential (Volt).
C. S cm⁻¹
Unit of electrical conductivity.
D. Debye
Unit of dipole moment.

🎯 Strategy

Used

Unit Identification

🧠 Memory Trick

Density = Mass ÷ Volume → g/mL

📚 Class XII Chemistry – Haloalkanes and Haloarenes – Physical Properties

17 Chloramphenicol is effective against typhoid fever. Structurally, it is an antibiotic that specifically contains which functional halogen?

A Fluorine

B Bromine

C Chlorine

D Iodine

💡 Short Explanation

Chloramphenicol is a halogen-containing antibiotic. The name itself indicates the presence of chlorine. It is used in the treatment of typhoid fever.

✅ Correct Answer Explanation

Chloramphenicol is a naturally occurring antibiotic that contains chlorine atoms in its molecular structure. It is produced by microorganisms and has historically been used for treating: Typhoid fever Certain bacterial infections The presence of chlorine makes it an important example of a naturally occurring organohalogen compound.

❓ Why Other Options Are Incorrect

A. Fluorine
Not present in chloramphenicol.
B. Bromine
Not present in chloramphenicol.
D. Iodine
Not present in chloramphenicol.

🎯 Strategy

Used

Name-Based Identification

🧠 Memory Trick

Chloro-phenicol → Contains Chlorine

📚 Class XII Chemistry – Haloalkanes and Haloarenes – Naturally Occurring Organohalogen Compounds

18 Which of the following best classifies chloroquine based on its origin and structural components?

A Natural polyhalogen compound

B Synthetic halogen compound

C Naturally occurring human hormone

D Anaesthetic gas

💡 Short Explanation

Chloroquine is a man-made drug. It contains halogen atoms in its structure. It is widely used as an antimalarial agent.

✅ Correct Answer Explanation

Chloroquine is a synthetic halogen compound used primarily for the treatment and prevention of malaria. Characteristics: Artificially synthesized. Contains halogen atoms. Important medicinal application of organohalogen chemistry. Therefore, it is classified as a synthetic halogen compound.

❓ Why Other Options Are Incorrect

A. Natural polyhalogen compound
Chloroquine is not naturally occurring.
C. Naturally occurring human hormone
Thyroxine is a hormone, not chloroquine.
D. Anaesthetic gas
Halothane is an anaesthetic, not chloroquine.

🎯 Strategy

Used

Classification-Based Recall

🧠 Memory Trick

Chloroquine = Synthetic Drug for Malaria

📚 Class XII Chemistry – Haloalkanes and Haloarenes – Applications of Organohalogen Compounds

19 In correlating structures to physical properties, why do para-isomers of dihalobenzenes have higher melting points than their ortho- and meta-isomers?

A High structural asymmetry

B Structural symmetry that fits better in a crystal lattice

C Extremely strong intermolecular hydrogen bonding

D Significantly lower molecular mass

💡 Short Explanation

Para-isomers are more symmetrical. Symmetrical molecules pack efficiently in crystals. Better packing increases melting point.

✅ Correct Answer Explanation

Among isomeric dihalobenzenes, para-isomers possess the highest degree of symmetry. Because of this symmetry: Molecules pack more efficiently in the crystal lattice. Crystal packing becomes more stable. More energy is required to break the lattice. Therefore, para-isomers generally exhibit higher melting points than corresponding ortho- and meta-isomers.

❓ Why Other Options Are Incorrect

A. High structural asymmetry
Para-isomers are highly symmetrical, not asymmetrical.
C. Extremely strong intermolecular hydrogen bonding
Dihalobenzenes do not exhibit hydrogen bonding.
D. Significantly lower molecular mass
All positional isomers have the same molecular mass.

🎯 Strategy

Used

Structure–Property Correlation

🧠 Memory Trick

Para = Perfect Packing = Higher Melting Point

📚 Class XII Chemistry – Haloalkanes and Haloarenes – Physical Properties

20 A key stereochemical outcome to comprehend is that SN2 reactions of optically active haloalkanes proceed specifically with:

A Retention of configuration

B Inversion of configuration

C Complete racemisation

D Beta-elimination

💡 Short Explanation

SN2 occurs through backside attack. The nucleophile attacks opposite to the leaving group. This causes inversion of configuration.

✅ Correct Answer Explanation

In an SN2 reaction, the nucleophile attacks the carbon atom from the side opposite to the leaving group. This mechanism: Occurs in a single step. Proceeds through backside attack. Produces Walden inversion (inversion of configuration). For optically active haloalkanes, the stereochemical outcome is therefore inversion of configuration.

❓ Why Other Options Are Incorrect

A. Retention of configuration
Not characteristic of the SN2 mechanism.
C. Complete racemisation
Commonly associated with SN1 reactions.
D. Beta-elimination
Refers to elimination reactions (E1/E2), not SN2 substitution.

🎯 Strategy

Used

Reaction Mechanism Analysis

🧠 Memory Trick

SN2 → Backside Attack → Inversion

📚 Class XII Chemistry – Haloalkanes and Haloarenes – Nucleophilic Substitution Reactions (SN2)

CUET UG Chemistry Booster Test -2 Introduction and Basic Concepts

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