Science (English Medium) Class 12 - CBSE Important Questions

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Draw the structures of the following molecules: XeF4

Appears in 23 question papers
Chapter: [0.07] P - Block Elements
Concept: P - Block Group 18 Elements > Concept of Group 18 Elements

Define a wavefront.

Appears in 16 question papers
Chapter: [0.1] Wave Optics
Concept: Introduction of Wave Optics

Define terms: Fuel cell

Appears in 15 question papers
Chapter: [0.02] Electrochemistry
Concept: Batteries > Primary Batteries

Write two important advantages of reflecting telescope over a refracting telescope.

Appears in 15 question papers
Chapter: [0.09] Ray Optics and Optical Instruments
Concept: Optical Instruments: Telescope

Illustrate the following reaction giving suitable example in each case:Gabriel phthalimide synthesis

Appears in 13 question papers
Chapter: [0.09] Amines
Concept: Amines > Preparation of Amines

Why are infra-red waves often called heat waves? Explain.

Appears in 13 question papers
Chapter: [0.08] Electromagnetic Waves
Concept: Electromagnetic Spectrum

Write the chemical equations involved in the following reactions:(i) Hoffmann-bromamide degradation reaction

Appears in 12 question papers
Chapter: [0.09] Amines
Concept: Amines > Preparation of Amines

Use Gauss' law to derive the expression for the electric field `(vecE)` due to a straight uniformly charged infinite line of charge density λ C/m.

Appears in 12 question papers
Chapter: [0.01] Electric Charges and Fields
Concept: Applications of Gauss’s Law

Write the equations involved in the following reactions:

Reimer-Tiemann reaction

Appears in 11 question papers
Chapter: [0.07] Alcohols, Phenols and Ethers
Concept: Chemical Properties of Phenol

Amino acids show amphoteric behaviour. Why?

Appears in 11 question papers
Chapter: [0.1] Biomolecules
Concept: Proteins > Amino Acids

A first-order reaction is 50% completed in 40 minutes at 300 K and in 20 minutes at 320 K. Calculate the activation energy of the reaction. (Given : log 2 = 0·3010, log 4 = 0·6021, R = 8·314 JK–1 mol–1)

Appears in 10 question papers
Chapter: [0.03] Chemical Kinetics
Concept: Temperature Dependence of the Rate of a Reaction

Draw the structures of the HClO3.

Appears in 10 question papers
Chapter: [0.07] P - Block Elements
Concept: P - Block Group 17 Elements > Oxoacids of Halogens

Write the chemical equations to illustrate the following name reaction: 

Cannizzaro’s reaction

Appears in 10 question papers
Chapter: [0.08] Aldehydes, Ketones and Carboxylic Acids
Concept: Aldehydes and Ketones > Chemical Reactions of Aldehydes and Ketones - Other Reactions

How do you convert the Toluene to Benzoic acid

Appears in 10 question papers
Chapter: [0.08] Aldehydes, Ketones and Carboxylic Acids
Concept: Acids > Nomenclature of Carboxylic Acids

Give reasons for the following:

Aniline does not undergo Friedel- Crafts reaction.

Appears in 10 question papers
Chapter: [0.09] Amines
Concept: Amines > Chemical Reactions of Amines - Electrophilic Substitution

Define the following terms: Essential amino acids

Appears in 10 question papers
Chapter: [0.1] Biomolecules
Concept: Proteins > Amino Acids

Why is bithional added to soap?

Appears in 10 question papers
Chapter: [0.16] Chemistry in Everyday Life
Concept: Cleansing Agents - Soaps

State the two Kirchhoff’s rules used in electric networks. How are there rules justified?

Appears in 10 question papers
Chapter: [0.03] Current Electricity
Concept: Kirchhoff’s Rules

In a single slit diffraction experiment, the width of the slit is made double the original width. How does this affect the size and intensity of the central diffraction band?

Appears in 10 question papers
Chapter: [0.1] Wave Optics
Concept: Diffraction of Light > The Single Slit

Give the truth table and circuit symbol for NAND gate

Appears in 10 question papers
Chapter: [0.14] Semiconductor Electronics - Materials, Devices and Simple Circuits
Concept: Digital Electronics and Logic Gates
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