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CBSE Important Questions

CBSE Guess > Papers > Important Questions > Class IX > 2009 > Science > Science By : Mr M. p. Keshri

CBSE CLASS I X

Atoms And Molecules (Solved)

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Q. 1. What is law of conservation of mass ?


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Q. 2. 100 g of 10% lead nitrate is mixed with 100 g of 10% sodium chloride solution in a closed container. 13.66 g of lead chloride is precipitated. The mixture contains 180 g of water and sodium nitrate. What amount of sodium nitrate is formed ?


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Q. 3. State and explain law of constant proportion.


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Q. 4. State and explain law of multiple proportions.


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Q. 5. State the postulates of Dalton’s atomic theory of matter.


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Q. 6. Explain the law of constant proportion on the basis of Dalton’s atomic theory.


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Q. 7. Water and hydrogen are two compounds of hydrogen and oxygen. Which law of Dalton is confirmed by this observation ?


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Q. 8. Write the drawbacks of Dalton’s atomic theory of matter.


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Q. 9. What is one major drawback of Dalton’s atomic theory of matter ?


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Q. 10. A sample of ammonia contains 28 g nitrogen and 6 g hydrogen. Another sample contains 15 g hydrogen. Find the amount of nitrogen in the second sample.


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Q. 11. In a reaction, 5.3 g of sodium carbonate reacted with 6 g of ethanoic acid. The products were 2.2 g of carbon dioxide , 0.9 g water and 8.2 g of sodium ethanoate. Show that these observations are in agreement with the law of conservation of mass.


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Q. 12. Hydrogen and oxygen combine in the ratio 1:8 by mass to form water. What mass of oxygen gas would be required to react completely with 3 g of hydrogen gas ?


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Q. 13. Which postulate of Dalton’s atomic theory is the result of the law of conservation of mass ?


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Q. 14. Which postulate of Dalton’s atomic theory can explain the law of definite proportions ?


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Q. 15. Define atom and give examples of atom.


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Q. 16.  What is the form of a atom that exists in a solid ?


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Q. 17. How the names of elements were derived ?


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Q. 18. Write the present accepted system of symbols of elements ?


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Q. 19. State the term “symbols” of elements.


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Q. 20. Give the significance of a symbol of an element with example.


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Q. 21. What is the significance of Na, the symbol of sodium ?


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Q. 22. Write the symbol of any five elements which is taken from their names in English.


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Q. 23. Write the symbol of some elements which is taken from their names from a language other than English.


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Q. 24. Write the symbol of following elements :

Argon, Arsenic, Barium, Boron, Cesium, Chromium, Cobalt, Neon, Platinum, Silicon.


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Q. 25. What is the contribution of Dalton’s atomic theory to the mass of atom ? How this issue were resolved ?


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Q. 26. State and explain atomic mass of an element.


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Q. 27. Define the atomic mass unit.


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Q. 28.  How do atoms exists ?


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Q.29. Why is it not possible to see an atom with naked eyes ?


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Q. 30. What are molecules ? How are atoms arranged in the molecules ?


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Q. 31.  Differentiate between a molecule and a compound.


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Q. 32. “A molecule is the smallest particle of a substance (element or compound) having the properties of the substance and is stable”. Comment.


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Paper By Mr. M. P. Keshari [ For Further Enquiry 09434150289]