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Science (English Medium) Class 12 - CBSE Important Questions

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Briefly describe the process of spermatogenesis.

Appears in 4 question papers
Chapter: [2] Human Reproduction
Concept: Gametogenesis

Mention any three characteristics of Neanderthal man that lived in near east and central Asia.

Appears in 4 question papers
Chapter: [6] Evolution
Concept: Human Evolution

Explain adaptive radiation with the help of a suitable example.

Appears in 4 question papers
Chapter: [6] Evolution
Concept: Adaptive Radiation

How is Hardy-Weinberg’s expression “(p2 + 2pq + q2) = 1” derived?

Appears in 4 question papers
Chapter: [6] Evolution
Concept: Hardy Weinberg’s Principle

List any two factors that can disturb the genetic equilibrium.

Appears in 4 question papers
Chapter: [6] Evolution
Concept: Hardy Weinberg’s Principle

Write the scientific name of the source plant and the part from which opiods are extracted. What is it commonly and chemically called?

Appears in 4 question papers
Chapter: [7] Human Health and Diseases
Concept: Types and Effects of Psychoactive Drugs >> Effects of Drug and Alcohol Abuse

What are methanogens?

Appears in 4 question papers
Chapter: [8] Microbes in Human Welfare
Concept: Microbes in Production of Biogas

Describe how do 'flocs' and 'activated sludge' help in Sewage Treatment.

Appears in 4 question papers
Chapter: [8] Microbes in Human Welfare
Concept: Microbes in Sewage Treatment

Why are baculoviruses considered good biocontrol agents?

Appears in 4 question papers
Chapter: [8] Microbes in Human Welfare
Concept: Microbes as Biocontrol Agents

Suggest two advantages to a farmer for using apomictic seeds of hybrid varieties.

Appears in 4 question papers
Chapter: [8] Strategies for Enhancement in Food Production
Concept: Strategies for Enhancement in Food Production (Questions)

Explain, giving three reasons, why tropics show greatest levels of species diversity.

Appears in 4 question papers
Chapter: [13] Biodiversity and Its Conservation
Concept: Patterns of Biodiversity

An element has atomic mass 93 g mol−1 and density 11.5 g cm–3. If the edge length of its unit cell is 300 pm, identify the type of unit cell. (NA = 6.023 × 1023 mol−1)

Appears in 4 question papers
Chapter: [1] Solid State
Concept: Number of Atoms in a Unit Cell

Calculate the number of unit cells in 8.1 g of aluminium if it crystallizes in a f.c.c. structure. (Atomic mass of Al = 27 g mol–1)

Appears in 4 question papers
Chapter: [1] Solid State
Concept: Number of Atoms in a Unit Cell

Give reasons:Ferrimagnetic substances show better magnetism than antiferromagnetic substances.

Appears in 4 question papers
Chapter: [1] Solid State
Concept: Properties of Solids: Magnetic Properties

Define the term: 

Ideal solution

Appears in 4 question papers
Chapter: [1] Solutions
Concept: Types of Solutions

Why are aquatic species more comfortable in cold water in comparison to warm water?

Appears in 4 question papers
Chapter: [1] Solutions
Concept: Colligative Properties and Determination of Molar Mass >> Reverse Osmosis and Water Purification

Calculate the degree of dissociation (α) of acetic acid if its molar conductivity (Λm) is 39.05 S cm2 mol−1.

(Given \[\ce{\lambda^{\circ}_{(H^+)}}\] = 349.6 S cm2 mol−1 and \[\ce{\lambda^{\circ}_{(CH_3COO^-)}}\] = 40.95 S cm2 mol−1)

Appears in 4 question papers
Chapter: [2] Electrochemistry
Concept: Conductance of Electrolytic Solutions >> Variation of Conductivity and Molar Conductivity with Concentration

Account for the following:

E° value for the Mn3+/Mn2+ couple is highly positive (+1.57 V) as compare to Cr3+/Cr2+.

Appears in 4 question papers
Chapter: [2] Electrochemistry
Concept: Galvanic Cells - Measurement of Electrode Potential

Which of the following cell was used in the Apollo space programme?

Appears in 4 question papers
Chapter: [2] Electrochemistry
Concept: Fuel Cells

For a reaction A + B ⟶ P, the rate is given by

Rate = k [A] [B]2

How is the rate of reaction affected if the concentration of B is doubled?

Appears in 4 question papers
Chapter: [3] Chemical Kinetics
Concept: Factors Influencing Rate of a Reaction
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