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Science (English Medium) Class 12 - CBSE Important Questions for Chemistry

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Assertion (A): Chlorobenzene is resistant to electrophilic substitution reaction.

Reason (R): C-Cl bond in chlorobenzene acquires partial double bond characters due to resonance.

Appears in 1 question paper
Chapter: [6] Haloalkanes and Haloarenes
Concept: Reactions of Haloarenes - Electrophilic Substitution Reactions

Inversion of configuration occurs in ______.

Appears in 1 question paper
Chapter: [6] Haloalkanes and Haloarenes
Concept: Reactions of Haloalkanes - Nucleophilic Substitution Reactions

Assertion: Chlorobenzene is resistant to nucleophilic substitution reaction at room temperature.

Reason (R): C–Cl bond gets weaker due, to resonance.

Appears in 1 question paper
Chapter: [6] Haloalkanes and Haloarenes
Concept: Reactions of Haloarenes - Nucleophilic Substitution

Why is the boiling point of o-dichlorobenzene higher than p-dichlorobenzene, but the melting point of para-isomer is higher than ortho-isomer?

Appears in 1 question paper
Chapter: [6] Haloalkanes and Haloarenes
Concept: Physical Properties of Haloalkanes and Haloarenes

Write the equation for the following:

Oxidation of chloroform by air and light.

Appears in 1 question paper
Chapter: [6] Haloalkanes and Haloarenes
Concept: Polyhalogen Compounds

Why haloarenes are not reactive towards nucleophilic substitution reaction? Give two reactions.

Appears in 1 question paper
Chapter: [6] Haloalkanes and Haloarenes
Concept: Reactions of Haloarenes - Nucleophilic Substitution

Arrange the isomeric dichlorobenzene in the increasing order of their boiling point and melting points.

Appears in 1 question paper
Chapter: [6] Haloalkanes and Haloarenes
Concept: Physical Properties of Haloalkanes and Haloarenes

Explain why the electrophilic substitution reactions in haloarenes occur slowly and require more drastic conditions as compared to those in benzene.

Appears in 1 question paper
Chapter: [6] Haloalkanes and Haloarenes
Concept: Reactions of Haloarenes - Electrophilic Substitution Reactions

An organic compound A with the molecular formula (+) C4H9Br undergoes hydrolysis to form (+) C4H9OH. Give the structure of A and write the mechanism of the reaction.

Appears in 1 question paper
Chapter: [6] Haloalkanes and Haloarenes
Concept: Reactions of Haloalkanes - Nucleophilic Substitution Reactions

What happens when 

(i) PCl5 is heated ? Write the reactions involved.

Appears in 1 question paper
Chapter: [7] P - Block Elements
Concept: Group 17 Elements - The Halogen Family >> Chlorine

Explain the mechanism of the following reaction:

Appears in 1 question paper
Chapter: [7] Alcohols, Phenols and Ethers
Concept: Preparation of Ethers

How will you convert: Propene to Propan-2-ol?

Appears in 1 question paper
Chapter: [7] Alcohols, Phenols and Ethers
Concept: Methods of Preparation of Alcohols

Account for the following: Fluorine does not exhibit positive oxidation state.

Appears in 1 question paper
Chapter: [7] P - Block Elements
Concept: Group 17 Elements - The Halogen Family

Account for the following: Oxygen shows catenation behavior less than sulphur.

Appears in 1 question paper
Chapter: [7] P - Block Elements
Concept: Group 16 Elements - The Oxygen Family

Pb(NO3)2 on heating gives a brown gas which undergoes dimerisation on cooling? Identify the gas

Appears in 1 question paper
Chapter: [7] P - Block Elements
Concept: Group 15 Elements - The Nitrogen Family >> Oxides of Nitrogen

Draw the structures of the following molecules: (HPO3)3

Appears in 1 question paper
Chapter: [7] P - Block Elements
Concept: Group 15 Elements - The Nitrogen Family >> Compounds of Phosphorus

What happens when: SO2 gas is passed through an aqueous solution Fe+3 salt?

Appears in 1 question paper
Chapter: [7] P - Block Elements
Concept: Group 16 Elements - The Oxygen Family >> Sulphur Dioxide

Write the final product(s) in each of the following reactions:

Appears in 1 question paper
Chapter: [7] Alcohols, Phenols and Ethers
Concept: Chemical Reactions of Alcohols and Phenols >> Reactions Involving Cleavage of Carbon–Oxygen (C–O) Bond in Alcohols

Give reasons: SO2 is reducing while TeO2 is an oxidising agent.

Appears in 1 question paper
Chapter: [7] P - Block Elements
Concept: Group 16 Elements - The Oxygen Family

Out of white phosphorus and red phosphorus, which one is more reactive and why?

Appears in 1 question paper
Chapter: [7] P - Block Elements
Concept: Group 15 Elements - The Nitrogen Family >> Phosphorus - Allotropic Forms
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