Test on Atom and Molecule

Test on Atom and Molecule for Class 9

Full Marks :40

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1. 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 ?     2

2. Write down the formulae of : (i) sodium oxide (ii) aluminium chloride (iii) sodium sulphide (iv) magnesium hydroxide .    2

3. 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. 2

4. Convert into moles :     6

(a) 12 g of oxygen gas

(b) 20 g of water

(c) 22 g of carbon dioxide

(Atomic masses : O = 16 u, H = 1 u and C = 12 u)

5. Calculate the number of molecules of sulphur (S8) present in 16 g of solid sulphur (Atomic mass of S = 32)    2

6. Calculate the number of aluminium ions present in 0.051 g of aluminium oxide. 2

(Hint. The mass of an ion is the same as that of an atom of the same element. Atomic mass of Al = 27 u)

7. Calculate the number of moles of magnesium present in a magnesium ribbon weighing 12 g. Molar atomic mass of magnesium is 24g mol–1.    2

8. The difference in the mass of 100 moles each of sodium atoms and sodium ions is 5.48002 g. Compute the mass of an electron. 3

9. Raunak took 5 moles of carbon atoms in a container and Krish also took 5 moles of sodium atoms in another container of same weight. (a) Whose container is heavier? (b) Whose container has more number of atoms?   3

10. A gold sample contains 90% of gold and the rest copper. How many atoms of gold are present in one gram of this sample of gold?   3

11. A sample of ethane (C2H6) gas has the same mass as 1.5 ×1020 molecules of methane (CH4). How many C2H6 molecules does the sample of gas contain?   3

12. A gold sample contains 90% gold and the rest copper. How many atoms of gold are present in one gram of this sample of gold?   3

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