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. 90. In a jar there are P moles of oxygen gas. The same jar contains hydrogen gas under similar conditions of temperature and pressure. How many moles of hydrogen are present in the jar ?
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Q. 91. Which of the following contains the most hydrogen atoms ?:
(i) 0.1 mole of CH4
(ii) 0.25 mole of H2O
(iii) 0.2 mole of NH3.
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Q. 92. Find the number of atoms in 1 g of zinc (atomic mass of zinc = 65.37). What is the weight of 1 atom of zinc ?
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Q. 93.How many moles are there in 5 g of hydrogen ?
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Q. 94. How many moles of chlorine atoms are there in one mole of the following ? :
(i) CaOCl2
(ii) BaCl2
(iii) AlCl3
(iv) CCl4
(v) FeCl3
(vi) Cl2O7.
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Q. 95. Calculate the mass of one molecule of water.
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Q. 96. 16.26 mg of a sample of an element ‘X’ contains 1.66 × 1020 atoms. Calculate the atomic mass of the element ‘X’.
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Q. 97. How many gram atoms of each element are present in 10 g of CaCO3.
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Q. 98. How many gram of Cr are there in 80 g of Cr2S3 ?
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Q. 99. The mass of an atom of element M is 3.05 × 10-22 g. Find its atomic weight. What can you say about the name of the element ?
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Q. 100.Calculate the molecular masses of H2, O2, Cl2, CO2, CH4, C2H6, C2H4, NH3, CH3OH.
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Q. 101. Calculate the formula unit masses of ZnO, Na2O, K2CO3; given atomic masses of Zn = 65 u, Na = 23 u, K = 39 u, C = 12 u and O = 16 u.
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Q. 102. If one mole of carbon atom weigh 12 grams, what is the mass (in grams) of one atom of carbon ?
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Q. 103. Which has more number of atoms, 100 grams of sodium or 100 grams of iron (given atomic mass of Na = 23 u, Fe = 56 u) ?
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Q. 104. A 0.24 g sample of compound of oxygen and boron was found by analysis to contain 0.096 g of boron and 0.144 g of oxygen. Calculate the percentage composition of the compound by weight.
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Q. 105. When 3 g of carbon is burnt in 8 g of oxygen, 11 g carbon dioxide is produced. What mass of carbon dioxide will be formed when 3 g of carbon is burnt in 50 g of oxygen ? Which law of chemical combination will govern your answer ?
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Q. 106. What are polyatomic ions ? Give examples.
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Q. 107. Write the chemical formula of the following :
(i) Magnesium chloride
(ii) Calcium oxide
(iii) Copper nitrate
(iv) Aluminium chloride
(v) Calcium carbonate
(vi) Carbon tetrachloride.
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Q. 108. Give the names of the elements present in the following compounds :
(i) Quick lime
(ii) Hydrogen bromide
(iii) Baking powder
(iv) Potassium sulphate.
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Q.109. Calculate the molar mass of the following substances :
(i) Ethyne, C2H2
(ii) Sulphur molecules, S8
(iii) Phosphorus molecule, P4 (atomic mass of phosphorus = 31)
(iv) Hydrochloric acid, HCl (v) Nitric acid, HNO3.
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Q. 110.What is the mass of :
(i) 1 mole of nitrogen atom ?
(ii) 4 moles of aluminium atoms (atomic mass of aluminium = 27) ?
(iii) 10 moles of sodium sulphite (Na2SO3) ?
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Q. 111. Convert into mole :
(i) 12 g of oxygen gas
(ii) 20 g of water
(iii) 22 g of carbon dioxide.
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Q. 112. What is the mass of :
(i) 0.2 g mole of oxygen atom ?
(ii) 0.5 mole of water molecule ?
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Q. 113. Calculate the number of molecules of sulphur (S8) present in 16 g of solid sulphur.
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Q. 114. Calculate the number of aluminium ions present in 0.051 g of aluminium oxide.
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