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, N_{2 }+ 3H_{2} = 2NH_{3}, 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 H_{2}

(ii) 2g N_{2}

(iii) 4g O_{2}

(iv) 11g CO_{2}

Answer:

2g N_{2}

Question 6.

Which of the following volume of the gas at NTP contains the largest number of molecules?

(i) 200 ml H_{2}

(ii) 100 ml O_{2}

(iii) 150 ml N_{2}

(iv) 22.5 ml NH_{3}

Answer:

200ml H^{2}

Question 7.

One of the following statements is not applicable to 1 mole of carbon dioxide :

(i) 22g CO_{2}

(ii) 22.4 lit of the gas

(iii) 1 gram atom of carbon and 2 gram atoms of oxygen

(iv) 6.023 × 10^{23} molecules of carbon dioxide

Answer:

22g CO_{2}

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 × 10^{23}

(ii) 1.5 × 10^{23}

(iii) 2.0 × 10^{23}

(iv) 3.5 × 10^{23}

Answer:

1.5 × 10^{23}

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) \(\frac{6.023}{23.4}\) × 10^{23}

(ii) 18 × 6.023 × 10^{2}

(iii) \(\frac{18}{22.4}\) × 10^{23}

(iv) 55.5 × 6.023 × 10^{23}

Answer:

55.5 × 6.023 × 10^{23}

Question 13.

Volume at NTP of 0.22 g of CO_{2 }is the same as that of

(i) 0.01 g of H_{2}

(ii) 0.085 g of NH_{3}

(iii) 320 mg of gaseous SO_{2}

(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 × 10^{23} g

Answer:

4 g

Question 15.

The molecular mass of CO_{2 }is 44 amu. Avogadro’s number is 6.023 × 10^{23}, therefore the mass of one molecule of CO_{2 }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 × 10^{23} atoms of hydrogen

(ii) 4 g} atoms of sodium

(iii) 6.023 × 10^{22} atoms of sodium

(iv) 4 moles of caustic soda

Answer:

6.023 × 10^{22} 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 N_{2}

(iv) 6.023 × 10^{24} molecules of oxygen

Answer:

24g of magnesium

Question 18.

One mole of CO_{2 }contains :

(i) 6.023 × 10^{23} atoms of carbon

(ii) 6.023 × 10^{23} atoms of oxygen

(iii) 18.1 × 10^{23} molecules of carbon dioxide

(iv) 3 gram atoms of carbon dioxide.

Answer:

6.023 × 10^{23} 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 CO_{2}

(iii) 46 g of CH_{3} OH

(iv) 54 g of N_{2} O_{5}

Answer:

34g water

Question 24.

The number of oxygen atoms in 4.4 g of CO_{2 }is approx:

(i) 1.2 × 10^{23}

(ii) 6 × 10^{23}

(iii) 6 × 10^{22}

(iv) 12 × 10^{23}

Answer:

1.2 × 10^{23}

Question 25.

The number of molecules in 16g of methane (CH_{4}) is :

(i) 3.0 × 10^{23}

(ii) 6.023 × 10^{23}

(iii) \(\frac{16}{6.023}\) × 10^{23}

(iv) \(\frac{16}{3}\) × 10^{23}

Answer:

6-023 × 10^{23}

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 kg^{2} C^{-12} isotope contains howmany C^{-12} atoms ?

(i) 12

(ii) 6.022 × 10^{23}

(iii) 1.66 × 10^{-24} g

(iv) 12 g atom.

Answer:

6.022 × 10^{23}

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 × 10^{23}

(ii) 6.022 × 10^{23}

(iii) 6.320 × 10^{23}

(iv) 6.029 × 10^{23}

Answer:

6.022 × 10^{23}

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 × 10^{23}

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 × 10^{23}

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 × 10^{23}

14. The molecular weight of chlorine is 71 . Clearly, 6.023 × 10^{23} 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 × 10^{23}

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

Answer:

3.0115 × 10^{23}

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

Answer:

12u

19. Between (i) 36g of H_{2}O and (ii) 46g of nitrogen dioxide, the larger number of molecules is in ______.

Answer:

36g H_{2}O

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:

12_{6} C

22. The volume occupied by 2g H_{2 }and 32g O_{2 }at STP is ______ cm_{3}.

Answer:

22400

23. The value 6.0233 × 10^{23} 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. (z_{1}) 16 g oxygen is equal to ______ moles of oxygen.

Answer:

0.5

28. (z_{2}) Atomic mass of element X 1 amu is ______ mass of one atom of the element.

Answer:

Actual.