IMPORTANT QUESTIONS

1. Q261 Tooth enamel is the hardest in our body. Name the compound of which it is made up of. At what pH of the mouth it gets corroded? State the role of bacteria present in mouth? Suggest a method to prevent tooth decay.

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2. Q262 Balance the following equations C₂H₂ + O₂ → CO₂ + H₂O

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3. Q263 Balance the following equations Na + O₂ → Na₂O

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4. Q264 What is the meaning of the effect of energy in an ecosystem? Explain with example how energy is lost at the various energy levels.

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5. Q265 Balance the following equations C₂H₂ + O₂ CO₂ + H₂O

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6. Q266 What happens chemically, when quicklime is added to water filled in a bucket?

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7. Q267 Write balanced chemical equations for the following reactions: Natural gas burns in air to form carbon dioxide and water.

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8. Q268 Placenta is a disc-like structure in the lining of the uterine wall. It contain villi on the embryo side of the tissues and blood space on the mother side surround the villi, Which of the following is not a true statement about a placenta?

   • (a)It is an organ that is found in all species
   • (b)It attaches the foetus to uterine wall
   • (c)Provide nutrients to the foetus
   • (d)It allow the foetus to transfer waste products to the mother bloodstream.

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9. Q269 The correct IUPAC name for CH₂=C(CH₂)-CH=CH₂ is

   • (a)2-methylbutane
   • (b)2-methyl, 1,3-butadiene
   • (c)1, 3-pentadiene
   • (d)2-methylbutene

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10. Q270 Two lenses have power of -4D What is the nature and focal length of each lens?

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