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