Atoms and Molecules

Atoms and Molecules - NCERT Guide Science Class 9

Q1: A 0.24 gm sample of compound of oxygen and boron was found by analysis to contain 0.096 gm of boron and 0.144 gm of oxygen. Calculate the percentagecomposition of the compound by weight.
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Q2: When 3.0 gm of carbon s burnt in 8.0 gm oxygen, 11.0 gm of carbon dioxide is produced. What mass of carbon dioxide will be formed when 3.0 gm of carbon is burnt in 50.00 gm of oxygen ? Which law of chemical combination will govern your answer ?
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Q3: What are polyatomic ions ? Give examples.
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Q4: Write chemical formulae of the following:
  1. Magnesium chloride
  2. Calcium oxide
  3. Calcium nitrate
  4. Aluminium
  5. chloride
  6. Calcium carbonate
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Q5: Give the names of the elements present in the following compounds:
  1. Quick lime
  2. Hydrogen bromide
  3. Baking powder
  4. Potassium sulphate
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Q6: What is the mass of:
  1. 1 mole of nitrogen atoms.
  2. 4 moles of aluminium atoms.
  3. 10 moles of sodium sulphite (Na2SO3).
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Q7: Convert into mole:
  1. 12 gm of oxygen gas
  2. 20 gm of water
  3. 22 gm of carbon dioxide
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Q8: What is the mass of :
  1. 0.2 mole of oxygen atoms
  2. 0.5 mole of water molecules
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Q9: Calculate the number of molecules of sulphur (S8) present in 16 gm of solid sulphur.
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Q10: Calculate the number of aluminium ions present in 0.51 gm of aluminium oxide.
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