10th Science Chemistry Assignment Answers 2021 TN SCERT Full Answer Key

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10th Science | Chemistry 

Unit 7 Atoms and Molecules

Assignment Answers 2021

TN SCERT Full Answer Key 

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  • Class:10
  • Subject: Science | Chemistry
  • UNIT-7 Atoms and Molecules

10th Chemistry -UNIT-7 Atoms and Molecules (Assignment Questions)

Part –A

 I. Choose the correct answer

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

 a) 17e¯ , 17p+, 17n

17e¯ , 20p+, 19n

 b) 18e¯ , 18p+, 17n

17e¯ , 17p+, 19n

c) 17e¯ , 17p+, 18n  

20e¯ , 20p+, 17n

d) 18e¯ , 17p+, 18n

17e¯ , 17p+, 20n  

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


d) 18

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

a) 46g b)


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


Part - B

II. Short Answer.

12. Define : Relative atomic mass

Relative atomic mass of an element is the ratio between the average mass of its isotopes to \(\frac{1}{12^{th}}\)part of the mass of a carbon-12 atom. It is denoted as Ar.

13.Give any two examples for heteroatomic molecules

  • HI, HCl, CO, HBr, HF.

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

Part – C

 III.Write In detail.

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

The salient features of “Modem atomic theory” are,
  • An atom is no longer indivisible.
  • Atoms of the same element may have different atomic mass.
  • Atoms of different elements may have the same atomic masses.
  • Atoms of one element can be transmuted into atoms of other elements. In other words, an atom is no longer indestructible.
  • Atoms may not always combine in a simple whole-number ratio.
  • Atom is the smallest particle that takes part in a chemical reaction.
  • The mass of an atom can be converted into energy [E = mc2].


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