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Science (English Medium) Class 12 - CBSE Important Questions

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Which allotrope of phosphorus is more reactive and why?

Appears in 3 question papers
Chapter: [7] P - Block Elements
Concept: Group 15 Elements - The Nitrogen Family >> Phosphorus - Allotropic Forms

How the supersonic jet aeroplanes are responsible for the depletion of ozone layers?

Appears in 3 question papers
Chapter: [7] P - Block Elements
Concept: Group 16 Elements - The Oxygen Family >> Ozone

F2 has lower bond dissociation enthalpy than Cl2. Why?

Appears in 3 question papers
Chapter: [7] P - Block Elements
Concept: Group 17 Elements - The Halogen Family

Which noble gas is used in filling balloons for meteorological observations?

Appears in 3 question papers
Chapter: [7] P - Block Elements
Concept: Group 18 Elements - The Noble gas Family

Complete the equation :​ XeF2+PF5 

Appears in 3 question papers
Chapter: [7] P - Block Elements
Concept: Group 18 Elements - The Noble gas Family

Give reasons for the following : Oxygen has less electron gain enthalpy with negative sign than sulphur.

Appears in 3 question papers
Chapter: [7] P - Block Elements
Concept: Group 16 Elements - The Oxygen Family

Give reasons for the following : H3PO2 is a stronger reducing agent than H3PO3.

 

Appears in 3 question papers
Chapter: [7] P - Block Elements
Concept: Group 15 Elements - The Nitrogen Family >> Oxoacids of Phosphorus

Which halogen compound in the following pair will react faster in SN2 reaction CH3Br or CH3I.

Appears in 3 question papers
Chapter: [7] P - Block Elements
Concept: Group 17 Elements - The Halogen Family

Which halogen compound in each of the following pairs will react faster in SN2 reaction

(CH3)3 C – Cl or CH3 – Cl

Appears in 3 question papers
Chapter: [7] P - Block Elements
Concept: Group 17 Elements - The Halogen Family

Draw the structure of the following:

H2SO4

Appears in 3 question papers
Chapter: [7] P - Block Elements
Concept: Group 16 Elements - The Oxygen Family >> Sulphuric Acid

What is meant by hydroboration-oxidation reaction? Illustrate it with an example.

Appears in 3 question papers
Chapter: [7] Alcohols, Phenols and Ethers
Concept: Methods of Preparation of Alcohols

Give reasons Thermal stability decreases from H2O to H2Te.

Appears in 3 question papers
Chapter: [7] P - Block Elements
Concept: Group 16 Elements - The Oxygen Family

Write the product(s) in the following reactions

Appears in 3 question papers
Chapter: [7] Alcohols, Phenols and Ethers
Concept: Physical Properties of Ethers

Write the product(s) in the following reaction

Appears in 3 question papers
Chapter: [7] Alcohols, Phenols and Ethers
Concept: Chemical Reaction of Ethers - Cleavege of C-O Bonds

Give simple chemical tests to distinguish between the following pairs of compounds :

Propanol and 2-methylpropan-2-ol

Appears in 3 question papers
Chapter: [7] Alcohols, Phenols and Ethers
Concept: Physical Properties of Ethers

Write the formula of reagents used in the following reactions :

Bromination of phenol to 2,4,6-tribromophenol

Appears in 3 question papers
Chapter: [7] Alcohols, Phenols and Ethers
Concept: Chemical Reaction of Ethers - Cleavege of C-O Bonds

Write the formula of reagents used in the following reactions :

Hydroboration of propene and then oxidation to propanol.

Appears in 3 question papers
Chapter: [7] Alcohols, Phenols and Ethers
Concept: Chemical Reaction of Ethers - Cleavege of C-O Bonds

Write the mechanism (using curved arrow notation) of the following reaction :

Appears in 3 question papers
Chapter: [7] Alcohols, Phenols and Ethers
Concept: Chemical Reactions of Alcohols and Phenols >> Reactions Involving Cleavage of Carbon–Oxygen (C–O) Bond in Alcohols

Complete the following chemical equation:

\[\ce{Ca3P2 + H2O ->}\]

Appears in 3 question papers
Chapter: [7] P - Block Elements
Concept: Group 15 Elements - The Nitrogen Family >> Phosphine

How do you prepare:

K2MnO4 from MnO2?

Appears in 3 question papers
Chapter: [7] P - Block Elements
Concept: Group 16 Elements - The Oxygen Family >> Classification of Oxides
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