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Science (English Medium) Class 12 - CBSE Important Questions

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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

How do cytokine barriers provide innate immunity in humans?

Appears in 6 question papers
Chapter: [7] Human Health and Diseases
Concept: Immunity

Name the source plant of heroin drug. How is it obtained from the plant?

Appears in 6 question papers
Chapter: [7] Human Health and Diseases
Concept: Types and Effects of Psychoactive Drugs >> Effects of Drug and Alcohol Abuse

Your advice is sought to improve the nitrogen content of the soil to be used for cultivation of a non-leguminous terrestrial crop.

  1. Recommend two microbes that can enrich the soil with nitrogen.
  2. Why do leguminous crops not require such enrichment of the soil? 
Appears in 6 question papers
Chapter: [8] Microbes in Human Welfare
Concept: Microbes as Biofertilizers

Give an example of a bacterium, a fungus and an insect that are used as biocontrol agents.

Appears in 6 question papers
Chapter: [8] Microbes in Human Welfare
Concept: Microbes as Biocontrol Agents

How has the development of bioreactor helped in biotechnology?

Appears in 6 question papers
Chapter: [9] Biotechnology - Principles and Processes
Concept: Principles of Processes of Biotechnology

Name the most commonly used bioreactor and describe its working.

Appears in 6 question papers
Chapter: [9] Biotechnology - Principles and Processes
Concept: Principles of Processes of Biotechnology

Explain the roles of the following with the help of an example each in recombinant DNA technology :

Restriction Enzymes

Appears in 6 question papers
Chapter: [9] Biotechnology - Principles and Processes
Concept: Tools of Recombinant DNA Technology >> Restriction Enzymes

Explain the roles of the following with the help of an example each in recombinant DNA technology :

Plasmids

Appears in 6 question papers
Chapter: [9] Biotechnology - Principles and Processes
Concept: Tools of Recombinant DNA Technology >> Competent Host (For Transformation with Recombinant DNA)

“India has greater ecosystem diversity than Norway.” Do you agree with the statement? Give reasons in support of your answer.

Appears in 6 question papers
Chapter: [13] Biodiversity and Its Conservation
Concept: Biodiversity

Write the difference between genetic biodiversity and species biodiversity that exists at all the levels of biological organisation.

Appears in 6 question papers
Chapter: [13] Biodiversity and Its Conservation
Concept: Biodiversity

Define azeotropes. 

Appears in 6 question papers
Chapter: [1] Solutions
Concept: Vapour Pressure of Liquid Solutions >> Vapour Pressure of Liquid- Liquid Solutions

What type of deviation is shown by a mixture of ethanol and acetone? Give reason.

Appears in 6 question papers
Chapter: [1] Solutions
Concept: Vapour Pressure of Liquid Solutions >> Vapour Pressure of Liquid- Liquid Solutions

State Kohlrausch’s law of independent migration of ions.

Appears in 6 question papers
Chapter: [2] Electrochemistry
Concept: Conductance of Electrolytic Solutions >> Variation of Conductivity and Molar Conductivity with Concentration

The following data were obtained during the first order thermal decomposition of SO2Cl2 at a constant volume :

SO2Cl2 (g) → SO2 (g) + Cl2 (g)

Experiment Time/s–1 Total pressure/atm
1 0 0.4
2 100 0.7

Calculate the rate constant.

(Given : log 4 = 0.6021, log 2 = 0.3010)

Appears in 6 question papers
Chapter: [3] Chemical Kinetics
Concept: Factors Influencing Rate of a Reaction

The conversion of molecules A to B follow second order kinetics. If concentration of A is increased to three times, how will it affect the rate of formation of B?

Appears in 6 question papers
Chapter: [3] Chemical Kinetics
Concept: Factors Influencing Rate of a Reaction

Give reasons:

Transition metals show variable oxidation states.

Appears in 6 question papers
Chapter: [4] d-block and f-block Elements
Concept: Physical Properties of the Transition Elements (d-block)

Complete the following equation : MnO4- + 8H+ + 5e- →

Appears in 6 question papers
Chapter: [4] d-block and f-block Elements
Concept: Important Compounds of Transition Elements
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