# WBBSE Class 9 Physical Science MCQ Questions Chapter 4.2 Mole Concept

Well structured WBBSE Class 9 Physical Science MCQ Questions Chapter 4.2 Mole Concept can serve as a valuable review tool before exams.

## Mole Concept Class 9 WBBSE MCQ Questions

Multiple Choice Questions :

Question 1.
Which scientist first gave the concept of molecule ?
(i) Dalton
(iii) Berzelius
(iv) Boyle

Question 2.
What is the volume of 1 gram-molecule of a gas or vapour at NTP ?
(i) 22.4 ml
(ii) 22.4 lit
(iii) 1000 ml
(iv) 2.24 lit
22.4 lit

Question 3.
In the reaction, N2 + 3H2 = 2NH3, the ratio of volumes of nitrogen, hydrogen and ammonia is 1 : 3 : 2. These figures illustrate the law of :
(i) constant proportion
(ii) multiple proportion
(iii) reciprocal proportion
(iv) Gay Lussac’s law of gaseous volumes
Gay Lussac’s law of gaseous volumes

Question 4.
At NTP, 5.6 lit of a gas weigh 8 grams. The vapour density of the gas is :
(i) 32
(ii) 40
(iii) 16
(iv) 8
16

Question 5.
Which of the following contains the least number of molecules ?
(i) 1g H2
(ii) 2g N2
(iii) 4g O2
(iv) 11g CO2
2g N2

Question 6.
Which of the following volume of the gas at NTP contains the largest number of molecules?
(i) 200 ml H2
(ii) 100 ml O2
(iii) 150 ml N2
(iv) 22.5 ml NH3
200ml H2

Question 7.
One of the following statements is not applicable to 1 mole of carbon dioxide :
(i) 22g CO2
(ii) 22.4 lit of the gas
(iii) 1 gram atom of carbon and 2 gram atoms of oxygen
(iv) 6.023 × 1023 molecules of carbon dioxide
22g CO2

Question 8.
A mole of any gas :
(i) always occupies one litre
(ii) always occupies 22.4 lit at NTP
(iii) can occupy any volume at NTP
(iv) always occupies 11.2 lit at NTP
Always occupies 22.4 lit at NTP

Question 9.
The latest standard of atomic weight is :
(i) Hydrogen = 1
(ii) Oxygen = 16
(iii) Carbon = 12
(iv) Nitrogen = 14
Carbon = 12

Question 10.
The approximate number of molecules in 4.25 g of ammonia is :
(i) 1.0 × 1023
(ii) 1.5 × 1023
(iii) 2.0 × 1023
(iv) 3.5 × 1023
1.5 × 1023

Question 11.
Atomic weight of chlorine is 35.5 . It has two isotopes of atomic weight 35 and 37 . What is the percentage of the heavier isotope in the sample?
(i) 5
(ii) 25
(iii) 20
(iv) 15
25

Question 12.
Number of molecules in one litre of water, is close to :
(i) $$\frac{6.023}{23.4}$$ × 1023
(ii) 18 × 6.023 × 102
(iii) $$\frac{18}{22.4}$$ × 1023
(iv) 55.5 × 6.023 × 1023
55.5 × 6.023 × 1023

Question 13.
Volume at NTP of 0.22 g of CO2 is the same as that of
(i) 0.01 g of H2
(ii) 0.085 g of NH3
(iii) 320 mg of gaseous SO2
(iv) All of the above
All of the above

Question 14.
Avogadro’s number of helium atoms weighs :
(i) 1 g
(ii) 4 g
(iii) 8 g
(iv) 4 × 6.023 × 1023 g
4 g

Question 15.
The molecular mass of CO2 is 44 amu. Avogadro’s number is 6.023 × 1023, therefore the mass of one molecule of CO2 is :
(i) 7.31 × 10-23
(ii) 3.65 × 10-23
(iii) 1.01 × 10-23
(iv) 2.01 × 10-23
7.31 × 10-23

Question 16.
4.0 grams of caustic soda contains :
(i) 6.023 × 1023 atoms of hydrogen
(ii) 4 g} atoms of sodium
(iii) 6.023 × 1022 atoms of sodium
(iv) 4 moles of caustic soda
6.023 × 1022 atoms of sodium

Question 17.
Which of the following weighs the least ?
(i) 24g of magnesium
(ii) 0.9 moles of nitric oxide
(iii) 22.4 lit of N2
(iv) 6.023 × 1024 molecules of oxygen
24g of magnesium

Question 18.
One mole of CO2 contains :
(i) 6.023 × 1023 atoms of carbon
(ii) 6.023 × 1023 atoms of oxygen
(iii) 18.1 × 1023 molecules of carbon dioxide
(iv) 3 gram atoms of carbon dioxide.
6.023 × 1023 atoms of carbon

Question 19.
One amu is :
(i) 1.00748 g
(ii) 0.000549 g
(iii) 1.66 × 10-24 g
(iv) 6.023 × 10-23 g
1.66 × 10-24 g

Question 20.
The vapour density of a gas is 11.2. The volume occupied by 11.2 g of the gas at NTP is :
(i) 1 L
(ii) 11.2 L
(iii) 22.4 L
(iv) 10 L
11.2 L

Question 21.
The vapour density of pure ozone would be :
(i) 16
(ii) 24
(iii) 32
(iv) 48
24

Question 22.
At STP 5.6 lit of a gas weighs 60g. The vapour density of the gas is :
(i) 30
(ii) 60
(iii) 120
(iv) 240
120

Question 23.
The largest number of molecules is in :
(i) 34 g water
(ii) 54 g oi CO2
(iii) 46 g of CH3 OH
(iv) 54 g of N2 O5
34g water

Question 24.
The number of oxygen atoms in 4.4 g of CO2 is approx:
(i) 1.2 × 1023
(ii) 6 × 1023
(iii) 6 × 1022
(iv) 12 × 1023
1.2 × 1023

Question 25.
The number of molecules in 16g of methane (CH4) is :
(i) 3.0 × 1023
(ii) 6.023 × 1023
(iii) $$\frac{16}{6.023}$$ × 1023
(iv) $$\frac{16}{3}$$ × 1023
6-023 × 1023

Question 26.
0.56 g of a gas occupies 280 ml at NTP, then its molecular mass is :
(i) 4.8
(ii) 44.8
(iii) 2
(iv) 22.4
448

Question 27.
‘Mole’ means
(i) a molecule
(ii) number of molecules
(iii) number of atoms
(iv) avogadro’s number of any particle

Question 28.
0.012 kg2 C-12 isotope contains howmany C-12 atoms ?
(i) 12
(ii) 6.022 × 1023
(iii) 1.66 × 10-24 g
(iv) 12 g atom.
6.022 × 1023

Question 29.
(i) Chemistry only
(ii) Physics only
(iii) Biology only
(iv) Chemistry, Physics and biology
Chemistry, physics and biology.

Question 30.
The value of Avogadro’s number is :
(i) 6.320 × 1023
(ii) 6.022 × 1023
(iii) 6.320 × 1023
(iv) 6.029 × 1023
6.022 × 1023

Question 31.
Formula unit mass of KCl is :
(i) 57.4 U
(ii) 45.7 U
(iii) 49.8 U
(iv) 74.5 U
74.5 U

Fill in the blanks :

1. Equal volumes of all gases under the same condition of temperature and pressure contain the same number of _______ .
molecules

2. Atomic weight of an element expressed in gram is called its ______ atomic weight.
gram

3. Avogadro’s number is ______ which is the fixed number of constituent particles present in 1 gram-molecule or in 1 gram or in 1 gram ion of any substance.
6.023 × 1023

4. Normal density = ______ density of a gas at NTP × 0.089
Vapour

5. Molecular weight of a gas = _______ × vapour density:
2

6. The gram-molecular volume of any gas or vapour occupies ______ litres at NTP.
22.4 lit

7. Molecules of elementary gases are ______.
diatomic

8. Molar volume is the volume of gram-molecular ______ of an element or a compound.
weight

9. The molecular mass of sulphuric acid is _______.
98

10. 22.4 litres of hydrogen at STP contain ______ number of hydrogen molecules.
6.023 × 1023

11. ______ was the first scientist who introduced the term molecule to indicate the smallest particle of both elements and compounds.

12. 2g of hydrogen and 32g of oxygen contain the _______ number of molecules.
same

13. The number of molecules contained in 8g of oxygen is ______.
1.505 × 1023

14. The molecular weight of chlorine is 71 . Clearly, 6.023 × 1023 atoms of chlorine weighs ______ grams.
35.5

15. The gram atoms contained in 5 g of calcium are ______.
0.125

16. The number of atoms present in 16 g of oxygen is ______.
6.023 × 1023

17. The number of gram moles present in 7g of CO is _______.
3.0115 × 1023

18. Only one atom of carbon is available from _______ of carbon.
12u

19. Between (i) 36g of H2O and (ii) 46g of nitrogen dioxide, the larger number of molecules is in ______.
36g H2O

20. The number of moles present in 90.0 g} of water is ______.
5

21. Modern atomic weights of elements are based on _____.
126 C

22. The volume occupied by 2g H2 and 32g O2 at STP is ______ cm3.
22400

23. The value 6.0233 × 1023 mol-1 is assigned to ______ constant.

24. The mass of one mole molecules of any substance is equal to ______.
Gram molecular mass

25. 12U of carbon contains how many atom of carbon.