» CBSE Science Practice Paper : Set IX : CBSE Sample Question Papers

Section – A

1. What is the density of mass of a typical white dwarf star ? 1
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2. What are enzymes ? Give an example. 1
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3. Write chemical name and formula of baking soda, 1
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4. Name the orbit of the satellites that help in satellite communication. 1
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5, Give chemical equation for reaction of acetone with HCN. 1
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6. Write the significance of Faraday’s Constant. 2
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7. Name some devices used to tap solar energy. Give two limitations in its use. 2
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8. Calculate pH of 0.01 M NaOH solution assuming it to be fully ionised in aqueous solution. 2
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9, A family consumes 14.5 Kg of LPG in 28 days. Calculate the average energy consumed per day if the calorific value of LPG is 55 kJ/g. 2
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10. A satellite orbits a planet in a radins ‘r’ Derive a relation for the velocity of satellite in the orbit. 2
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11. Complete the following reactions :

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12. A star of mass 100 times that of the sun has come to red giant phase. Explain the next two phases in its life. 3
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13. Write structural formula of ethanoic acid. What is common name of pure ethanoic acid ? How will you prepare it from methanol ? Give chemical reaction involved and one use of ethanoic acid.

OR
{a) What is gypsum ? What happens when gypsum is heated to 373 K ?
(b) Define ‘calorific value of a fuel’. Amongst the following fuels, which one has the highest calorific value ?
C₂H₅OH,CH₄,C₂H₂.
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14. Two resistors 2Ω and 5Ω are connected as shown in the circuit.
Find (i) current drawn from cell,

(ii) Heat produced in each resistor in 2 minutes.

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If 2Ω and 5Ω resistors are connected in parallel to a 10 V cell, find (i) current in each resistor, (ii) ratio of heat produced in them. 3
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15. Write the reaction that takes place in a nuclear reactor. What is meant by enrichment of fuel ? When is a nuclear reactor said to have become critical ? 3
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