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Science (English Medium) Class 12 - CBSE Important Questions

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Explain the effect on the characteristics of a river when urban sewage is discharged into it.

Appears in 7 question papers
Chapter: [13] Biodiversity and Its Conservation
Concept: Biodiversity

Name any two biodiversity hot spots in India.

Appears in 7 question papers
Chapter: [13] Biodiversity and Its Conservation
Concept: Loss of Biodiversity

What type of azeotrope is formed by positive deviation from Raoult’s law?

Appears in 7 question papers
Chapter: [1] Solutions
Concept: Vapour Pressure of Liquid Solutions >> Vapour Pressure of Liquid- Liquid Solutions

Define the following term:

Fuel cell

Appears in 7 question papers
Chapter: [2] Electrochemistry
Concept: Electrochemical Cells

How would you account for the following: Transition metals form complex compounds.

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

Account for the following:

E° value for the Mn3+/Mn2+ couple is much more positive than that for Cr3+/Cr2+.

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

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 reason for the following:

The transition metals generally form coloured compounds.

Appears in 7 question papers
Chapter: [4] d-block and f-block Elements
Concept: Physical 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: 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: 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: 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: Classification of Vitamins

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

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 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
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