CLASS-9 HOLIDAY H W
LESSON-3 ATOMS AND MOLECULES(A-4 SIZE PAPER)
LESSON-3 ATOMS AND MOLECULES(A-4 SIZE PAPER)
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1
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What is an atom?
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2
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How many atoms are present in one molecule of ozone?
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3
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Define the law of constant proportion.
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4
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What is the ratio between masses of (a) hydrogen and
oxygen in H2O (b) nitrogen and hydrogen in NH3? [Atomic
mass of H = 1 u, O = 16 u, N = 14 u]
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5
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What is the ratio between masses of carbon and oxygen in
CO2?
[Atomic mass of C = 12 u, O = 16 u] |
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6
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As per the law of definite proportions carbon and oxygen
combine in a ratio of 3 : 8. Compute the mass of oxygen gas that would be
required to react completely with 6 g carbon.
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7
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Name the anion and cation which constitute the molecule of
magnesium oxide.
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8
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Name the international organisation which approves the
name given to the elements.
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9
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The oxide of aluminium has a chemical formula Al2O3.
State the valency of Al.
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10
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Write the names of the following compounds:
(a) Al2(SO4)3 (b) NH4OH |
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11
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What is the formula of ammonium chloride?
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12
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(a) Define atomic mass unit.
(b) 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 4 g of hydrogen gas? |
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13
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(a) Give one word for the following:
(i) Positively charged ion (ii) A group of atoms carrying a charge. (b) Mention any two important rules for writing a chemical formula. |
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14
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(a) How would you differentiate between a molecule of an
element and a molecule of a compound? Write one example of each type.
(b) Write the chemical formula of baking soda. |
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15
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Define atomicity. Give an example of each of monoatomic,
diatomic, tetra-atomic and polyatomic molecules.
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16
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Classify the following compounds as diatomic, triatomic
and polyatomic molecules:
HCl, H2, H2O and NH3. |
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17
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How will you prove experimentally the law of conservation
of mass?
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18
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(a) When 5 g of calcium is burnt in 2 g of oxygen then 7 g
of calcium oxide is produced. What mass of calcium oxide will be produced
when 5 g of calcium is burnt in 20 g of oxygen. Which law of chemical
combination will govern your answer? State the law.
(b) Write the chemical formula of calcium oxide. |
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19
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(i) Write the full form of IUPAC.
(ii) Hydrogen and oxygen combine in the ratio of 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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20
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Write the formulae of
(a) Magnesium hydroxide (b) Hydrogen sulphide (c) Potassium chloride (d) Calcium oxide (e) Barium chloride (f) Sodium carbonate |
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21
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An element ‘X’ forms an oxide with formula X2O3
(a) State the valency of X. (b) Write the formula of (i) chloride of X, (ii) sulphate of X. |
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22
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Using criss-cross method, write the chemical formulae of
copper chloride, calcium sulphate and sodium phosphate.
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23
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(a) What are polyatomic ions?
(b) Write the formulae and names of the compounds formed by combination of (i) Fe3+ and SO42– (ii) NH4+ and CO32– |
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24
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Write the formulae of:
(a) Sodium chloride (b) Aluminium oxide (c) Ammonium sulphate |
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25
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(a) Define polyatomic ion.
(b) Write the name of the compound (NH4)2SO4 and mention the ions present in it. |
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