Assignment

Class-10 Subject: SCIENCE

UNIT – VII- Atoms and Molecules

• Part - A

I.One Mark Questions

1. Number of electrons, protons and neutrons present in 17Cl35, 17Cl37 is-

--------------

a) 17e¯ , 17p+, 17n

 17e¯ , 17p+, 19n

b) 18e¯ , 18p+, 17n

 17e¯ , 20p+, 19n

c) 17e¯ , 17p+, 18n

 17e¯ , 17p+, 20n

d) 18e¯ , 17p+, 18n

20e¯ , 20p+, 17n

2. Isobars are defined as---------

a) Elements show same atomic number with different mass number

b) Elements show same mass number with different atomic number

c) Elements show same valency

d) None of these

3. The Atomicity of Glucose molecule is ________.

a) 6       b) 12       c)24        d) 18

4. The mass of 5 moles of sodium is -------------

a) 46g b) 34g c) 105g d) 115g

5. Number of atoms present in 3 moles of iron is--------

a) 6.023 x 1023 b) 18.069 x 1023 c) 12.046 x 1023

 d) None

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Part – B

II. Short Answer.

6. Define : Relative atomic mass

• Relative atomic mass of an element is the ratio between the average mass of its isotopes to 1 / 12th part of the mass of a carbon – 12 atom. It is denoted as Ar.

•  Relative atomic mass =  Average mass of the isotopes of the element / 1/12th  of the mass of one Carbon- 12 atom

7. Give any two examples for heteroatomic molecules

• Heterodiatomic molecules.

e.g.,

• HCl
• NaCl.

8. Calculate the number of moles in 46 g of Sodium?

9.Calculate the mass of the5×1023molecules of Glucose.

10.Calculate the number of molecules in 11.2 litre of CO2 at S.T.P.

Part – C

III. Write in detail.

1. Give the salient features of “Modern Atomic Theory”.

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