• +91 9971497814
  • info@interviewmaterial.com

Chapter 3 Atoms And Molecules Interview Questions Answers

Question 1 :
In a reaction, 5.3 g of sodium carbonate reacted with 6 g of ethanoic acid. The products were 2.2 g of carbon dioxide, 0.9 g of water and 8.2 g of sodium ethanoate. Show that these observations are in agreement with the law of conservation of mass.
Sodium carbonate + ethanoic acid → sodium ethanoate + carbon dioxide + water

Answer 1 :

Total mass of reactants = mass of sodium carbonate + mass of ethanoic acid
= 5 – 3 g + 6 g = 11.3 g
Total mass of products = mass of sodium ethanoate + mass of carbon dioxide + mass of water
= 8.2 g + 2.2 g + 0.9 g = 11.3 g
Thus, the mass of reactants is equal to the mass of products, therefore the observations are in agreement with the law of conservation of mass.

Question 2 :
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?

Answer 2 :

∵ 1 g of hydrogen reacts with = 8 g of oxygen
∴ 3 g of hydrogen reacts with = 8 × 3 = 24 g of oxygen
Thus, 24 g of oxygen gas would be required to react completely with 3 g of hydrogen gas.

Question 3 :
Which postulate of Dalton’s atomic theory is the result of the law of conservation of mass?

Answer 3 :

The postulate that “atoms can neither be created nor destroyed in a chemical reaction” is the result of the law of conservation of mass.

Question 4 :
Which postulate of Dalton’s atomic theory can explain the law of definite proportions?

Answer 4 :

The postulate that “A chemical compound always consists of the same elements combined together in the same proportion by mass” is the law of definite proportions.

Question 5 :
Define the atomic mass unit.

Answer 5 :

Atomic mass unit is defined as the mass unit equal to exactly one-twelfth (1/12th) of the mass of one atom of carbon-12. It is denoted by u (unified mass).
i.e. 1 u = 1.66 × 10-24 g

Question 6 :
Why is it not possible to see an atom with naked eyes?

Answer 6 :

It is not possible to see an atom with naked eye because of its extremely small size (atomic radius is of the order of 10-10 m).

Question 7 :
Write down the formula of

sodium oxide’
aluminium chloride
sodium sulphide
magnesium hydroxide.

Answer 7 : Sodium oxide


Aluminium chloride
Sodium sulphide

Magnesium hydroxide

Question 8 : Write down the names of compounds represented by the following formulae:

1.   AI2(S04)3

2.   CaCI2

3.   K2S04

4.   KNO3

5.   CaCO3

Answer 8 :

(i) Aluminium sulphate
(ii) Calcium chloride
(iii) Potassium sulphate
(iv) Potassium nitrate
(v) Calcium carbonate

Question 9 :
What is meant by the term chemical formulae?

Answer 9 :

The chemical formula of a compound is a symbolic representation of its composition. e.g., formula of calcium oxide.
Thus, chemical formula of calcium oxide is CaO.

Question 10 : How many atoms are present in a
(i) H2S molecule and
(ii) 
 ion?


Answer 10 : (i) 3 atoms because H2S molecule has two atoms of hydrogen and one atom ofsulphur.
(ii) 5 atoms because 
 ion has one atom of phosphorus and four atoms ofoxygen.


Selected

 

Chapter 3 Atoms And Molecules Contributors

krishan

Share your email for latest updates

Name:
Email:

Our partners