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
(ii) Avogadro
(iii) Berzelius
(iv) Boyle
Answer:
Avogadro

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
Answer:
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
Answer:
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
Answer:
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
Answer:
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
Answer:
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
Answer:
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
Answer:
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
Answer:
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
Answer:
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
Answer:
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
Answer:
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
Answer:
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
Answer:
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
Answer:
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
Answer:
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
Answer:
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.
Answer:
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
Answer:
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
Answer:
11.2 L

Question 21.
The vapour density of pure ozone would be :
(i) 16
(ii) 24
(iii) 32
(iv) 48
Answer:
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
Answer:
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
Answer:
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
Answer:
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
Answer:
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
Answer:
448

Question 27.
‘Mole’ means
(i) a molecule
(ii) number of molecules
(iii) number of atoms
(iv) avogadro’s number of any particle
Answer:
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.
Answer:
6.022 × 10²³

Question 29.
Avogadro’s number is used in
(i) Chemistry only
(ii) Physics only
(iii) Biology only
(iv) Chemistry, Physics and biology
Answer:
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
Answer:
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
Answer:
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 _______ .
Answer:
molecules

2. Atomic weight of an element expressed in gram is called its ______ atomic weight.
Answer:
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.
Answer:
6.023 × 10²³

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

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

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

7. Molecules of elementary gases are ______.
Answer:
diatomic

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

23. The value 6.0233 × 10²³ mol^-1 is assigned to ______ constant.
Answer:
Avogadro’s.

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

25. 12U of carbon contains how many atom of carbon.
Answer:
Only one atom of carbon.

26. 1 mole of carbon contains ________.
Answer:
12 g of C.

27. (z₁) 16 g oxygen is equal to ______ moles of oxygen.
Answer:
0.5

28. (z₂) Atomic mass of element X 1 amu is ______ mass of one atom of the element.
Answer:
Actual.