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Science (English Medium) Class 12 - CBSE Important Questions

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Write one similarity and one difference between the chemistry of lanthanoid and actinoid elements.

Appears in 7 question papers
Chapter: [4] d-block and f-block Elements
Concept: F-block Elements >> The Actinoids

Give reasons for the following:

The transition metals generally form coloured compounds.

Appears in 7 question papers
Chapter: [4] d-block and f-block Elements
Concept: General Properties of the Transition Elements (d-block)

On the basis of crystal field theory, write the electronic configuration for d4 ion if ∆0 < P.

Appears in 7 question papers
Chapter: [5] Coordination Compounds
Concept: Bonding in Coordination Compounds >> Crystal Field Theory (CFT)

Explain the following reaction:

Wolff-Kishner reduction

Appears in 7 question papers
Chapter: [8] Aldehydes, Ketones and Carboxylic Acids
Concept: Concepts of Aldehydes, Ketones, and Carboxylic Acids >> Chemical Reactions of Aldehydes and Ketones - Reduction

Explain the following reaction:

Cannizzaro reaction

Appears in 7 question papers
Chapter: [8] Aldehydes, Ketones and Carboxylic Acids
Concept: Concepts of Aldehydes, Ketones, and Carboxylic Acids >> Chemical Reactions of Aldehydes and Ketones - Other Reactions

Write chemical test to distinguish between the following compounds:

Phenol and Benzoic acid

Appears in 7 question papers
Chapter: [8] Aldehydes, Ketones and Carboxylic Acids
Concept: Concepts of Aldehydes, Ketones, and Carboxylic Acids >> Chemical Reactions of Aldehydes and Ketones - Oxidation

Why vitamin C cannot be stored in our body?

Appears in 7 question papers
Chapter: [10] Biomolecules
Concept: Biomolecules in the Cell > Vitamins >> Classification of Vitamins

Find the distance of the point (−1, −5, −10) from the point of intersection of the line `vecr=2hati-hatj+2hatk+lambda(3hati+4hatj+2hatk) ` and the plane `vec r (hati-hatj+hatk)=5`

Appears in 7 question papers
Chapter: [11] Three - Dimensional Geometry
Concept: Three - Dimensional Geometry Examples and Solutions

Draw a necessary arrangement for winding of primary and secondary coils in a step-up transformer. State its underlying principle and derive the relation between the primary and secondary voltages in terms of number of primary and secondary turns. Mention the two basic assumptions used in obtaining the above relation.

Appears in 7 question papers
Chapter: [6] Electromagnetic Induction
Concept: Inductance >> Mutual Inductance

Why does an unpolarised light incident on a polaroid get linearly polarised ?

Appears in 7 question papers
Chapter: [10] Wave Optics
Concept: Polarisation

Draw graphs showing variation of photoelectric current with applied voltage for two incident radiations of equal frequency and different intensities. Mark the graph for the radiation of higher intensity.

Appears in 7 question papers
Chapter: [11] Dual Nature of Radiation and Matter
Concept: Experimental Study of Photoelectric Effect

Draw a circuit diagram of a transistor amplifier in CE configuration.

Appears in 7 question papers
Chapter: [14] Semiconductor Electronics - Materials, Devices and Simple Circuits
Concept: Junction Transistor >> Transistor as an Amplifier (Ce-configuration)

Draw a diagram of the mature embryo sac of an angiospermic ovule and label any four parts in it.

Appears in 6 question papers
Chapter: [1] Sexual Reproduction in Flowering Plants
Concept: Development of Female Gametophyte or Embryo Sac

Medically it is advised to all young mothers that breast-feeding is the best for their newborn babies. Do you agree? Give reasons in support of your answer.

Appears in 6 question papers
Chapter: [2] Human Reproduction
Concept: Pregnancy and Embryonic Development

Explain menstrual cycle in human females.

Appears in 6 question papers
Chapter: [2] Human Reproduction
Concept: Menstrual Cycle (Ovarian Cycle)

How can the scientific understanding of the menstrual cycle of human females help as a contraceptive measure?

Appears in 6 question papers
Chapter: [2] Human Reproduction
Concept: Menstrual Cycle (Ovarian Cycle)

Explain the mechanism of 'sex determination' in birds. How does it differ from that of human beings?

Appears in 6 question papers
Chapter: [4] Principles of Inheritance and Variation
Concept: Sex Determination

Write the names of the following:

A 15 mya primate that was ape-like

Appears in 6 question papers
Chapter: [6] Evolution
Concept: Human Evolution

Write the names of the following:

A 2 mya primate that lived in East African grasslands

Appears in 6 question papers
Chapter: [6] Evolution
Concept: Human Evolution

With the help of an algebraic equation, how did Hardy-Weinberg explain that in a given population the frequency of occurrence of alleles of a gene is supposed to remain the same through generations?

Appears in 6 question papers
Chapter: [6] Evolution
Concept: Hardy Weinberg’s Principle
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