Science 2008 CBSE [ All India ] Set III
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Q1
How does the flow of acid rain water into a river make the survival of aquatic life in the river difficult?
Marks:1View AnswerAnswer:
Flow of acid rain water into a river makes the survival of aquatic life in the river difficult because it lowers the pH of the river water and living organisms an survive only in a narrow range of pH (7 to 7.8).
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Q2
Balance the following equation:
MnO2 + HCl
MnCl2 + Cl2 + H2OMarks:1View AnswerAnswer:
MnO2 +4 HCl
MnCl2 + Cl2 + 2H2O -
Q3
Why is respiration considered an exothermic process?
Marks:1View AnswerAnswer:
Respiration is the oxidation of food to release energy. Since energy is released in the process of respiration, that is why it is considered an exothermic reaction.
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Q4
Why is a series arrangement not used for connecting domestic electrical appliances in a circuit?
Marks:1View AnswerAnswer:
A series arrangement is not used for connecting domestic electrical appliances in a circuit because in case, one of the components of the circuit fails, current in other appliances would be affected and none of the components works.
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Q5
Out of 60W and 40W lamps, which one has a higher electrical resistance when in use?
Marks:1View AnswerAnswer:
A 40W lamp has a higher resistance due to the fact that power is inversely proportional to the resistance at constant potential difference.
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Q6
Draw the following diagram in your answer-book and show the formation of image with the help of suitable rays.
Marks:1View AnswerAnswer:
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Q7
How do autotrophs obtain CO2 and N2 to make their food?
Marks:1View AnswerAnswer:
Autotrophs obtain CO2 from air through stomata and N2 from soil in the form of nitrates through roots.
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Q8
Which one of the following gases is the major constituent of biogas? Carbon monoxide, Hydrogen, Methane, Carbon dioxide
Marks:1View AnswerAnswer:
Methane is the major constituent of biogas.
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Q9
What is the effect of DNA copying which is not perfectly accurate on the reproduction process?
Marks:1View AnswerAnswer:
DNA copying which is not perfectly accurate will give rise to new variations which will be transferred to the offspring during reproduction.
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Q10
Draw ray diagrams to represent the nature, position and relative size of the image formed by a convex lens for the object placed:
(a) at 2F1
(b) between F1 and the optical center O of lens.Marks:2View AnswerAnswer:
(b)
