WBBSE For Class 9 Physical Science And Environment Concept Of Mole MCQS

Concept Of Mole MCQs

Question 1. 1 mole is the number of atoms in exactly

1. 1g of  ¹²C
2. 12 g of ¹²C
3. 1/12 g of ¹²C
4. None of these

Answer: (2) 12 g of ¹²C

Question 2. The mass of a C^-12 atom is

1. 12g
2. 1/12 g
3. 12/ N_A g
4. 12 × N_A g 

Answer: (3)  12/ N_A g

Read And Learn More WBBSE Solutions For Class 9 Physical Science And Environment MCQS

Question 3. The number of moles (n), the number of particles (N) and the Avogadro number (N_A) are related as

1. n =N_A/N
2. N/N_A=N
3. n = N/N_A
4.  n = N.N_A

Answer: (3) n = N/N_A

Question 4. 16 g of oxygen is the mass of oxygen of

1. One oxygen atom
2. One oxygen molecule
3. 1-mole oxygen molecule
4. One-mole oxygen atom

Answer: (4) One-mole oxygen atom

WBBSE Class 9 concept of mole MCQs with answers

Question 5. 6.4 g of oxygen is equivalent to

1. 0.4 mol of oxygen atoms
2. 0.4 mol of oxygen molecules.
3. 0.2 mol of oxygen atoms
4. None of these

Answer. (1) 0.4 mol of oxygen atoms

Question 6. 0.10 mol of carbon is equivalent to

1.  1.2 g of carbon
2. 1/12 g of carbon
3. 12.0 g of carbon
4. 0.1 g of carbon

Answer:(1) 1.2 g of carbon

Question 7. A sample is known to contain 2 x 6.022 x 10²³. hydrogen atoms. How many mol hydrogen atoms does it contain?

1. 1 mol
2. 1/2 mol
3. 2 mol
4. N_A mol

Answer: (3) 2 mol

Question 8. Formula mass of water (H₂O) is

1. 33
2. 17
3.  10
4. 18

Answer: (4) 18

Concept of mole multiple choice questions for WBBSE Class 9

Question 9. Consider two gases A and B or ideal gas with M_A > M_B. The molar volumes (Vm) at given pressure and temperature are like

1. V_m(A)= V_m(B)
2. V_m(A)> V_m(B)
3. V_m(A) <V_m(B)
4. No relation

Answer: (1) V_m(A)= V_m(B)

Question 10.A sample contains m g of a compound X (mx = molar mass). The sample contains n mol of X. Then n, m and M are related as

1. M=m.n
2. M= n/n
3. M= n/m
4.  n=m.M

Answer: (2) M = m/n

Question 11. ‘Mole’ means

1. A molecule
2. Number of molecules
3. Number of atoms
4. Avogadro’s number of any particle

Answer: (4) Avogadro’s number of any particle

Question 12. 0.012 kg of C^-12isotope contains how many C^-12atoms ?

1. 12
2. 6.022 x10²³
   
3. 1.66 x10^-24 g
4. 12 g atom .

Answer: (2) 6.022 x10²³

Important mole concept questions for Class 9 Physical Science

Question 13. Avogadro’s number is used in

1. Chemistry only
2.  Physics only
3. Biology only
4. Chemistry, physics and biology

Answer: (4) Chemistry, physics and biology

Question 14. Unit of relative atomic mass is

1. Gram
2. Kilogram
3. a.m.u.
4. No unit

Answer: (4) No unit

Question 15. Which scientist first gave the concept of molecule?

1.  Dalton
2. Avogadro
3. Berzilius
4. Boyle

Answer: (2) Avogadro

WBBSE Class 9 Physical Science MCQs on mole and molar mass

Question 16. What is the volume of 1 gram-molecule of a gas or vapour at NTP?

1. 22.4 ml
2. 22.4 lit
3.  1000 ml
4. 2.24 lit

Answer: (2) 22.4 lit

Question 17. 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

1. Constant proportion
2. Multiple proportion
3. Reciprocal proportion
4.  Gay Lussac’s law of gaseous volumes

Answer: (4) Gay Lussac’s law of gaseous volumes

Question 18. At NTP, 5.6 lit of a gas weighs 8 grams. The vapour density of the gas is 

1.  32
2. 40
3. 16
4. 8

Answer: (3) 16

Solved MCQs on mole concept for WBBSE Class 9

Question 19. Which of the following contains the least number of molecules?

1. 19 H₂
2. 2g N₂
3. 4g O₂
4.  11g CO₂

Answer: (2) 2g N₂

Question 20. Which of ‘the following volumes of the gas at NTP contains the largest number of molecules?

1. 200 ml H₂
2.  100 ml O₂
3. 150 ml N₂
4. 22.5 ml NH₃

Answer: (1) 200 ml H₂,

Question 21. Which one of the following statements is not applicable to 1 mole of carbon dioxide?

1. 22 g CO₂
2. 22.4 lit of the gas
3. 1 gram atom of carbon and 2 gram atoms of oxygen
4. 6.023 x 10²³ molecules of carbon dioxide

Answer: (1) 22 g CO₂

Mole-mass and mole-volume relationship MCQs Class 9 WBBSE

Question 22. A mole of any gas 

1. Always occupies one liter
2. Always occupies 22.4 lit at NTP
3. Can occupy any volume at NTP
4. Always occupies 11.2 lit at NTP

Answer: (2) Always occupies 22.4 lit at NTP

Question 23. The latest standard of atomic weight is 

1. Hydrogen = 1
2. Oxygen = 16
3. Carbon = 12
4. Nitrogen = 14

Answer: (3) Carbon = 12

Question 24. The approximate number of molecules in 4.25 g of ammonia is 

1. 1.0 x 10²³
2. 1.5 x 10²³
3. 2.0 x 10²³
4. 3.5 x 10²³

Answer: (2) 1.5 x 10²³

Best multiple choice questions on mole concept for WBBSE Class 9

Question 25. Atomic weight of chlorine is 35.5. It has two isotopes of atomic weights 35 and 37. What is the percentage of the heavier isotope in the sample?

1. 5
2. 25
3. 20
4. 15

Answer: (2) 25

Question 26 Number of molecules in one litre of water is close to 

1. \(\frac{6.023}{23.4} \times 10^{23}\)
2. 18 x 6.023 x 10²³
3. \(\frac{18}{22.4} \times 10^{23}\)
4. 55.5 x 6.023 x 10²³

Answer: (4) 55.5 x 6.023 x 10²³

Question 27. Volume at NTP of 0.22 g of CO₂ is the same as that of 

1. 0.01 g of H₂
2. 0.085 g of NH₃
3. 320 mg of gaseous SO₂
4. All of the above

Answer: (4) All of the above

Question 28. Avogadro’s number of helium atoms weighs 

1. 1 g
2. 4 g
3. 8 g
4. 4 x 6.025 x10²³ g

Answer: (2) 4 g

Question 29. The molecular mass of CO₂ is 44 a.m.u. Biotec? s number is 6.023 x 10²³, therefore, the mass of one molecule of CO₂ , is

1.  7.31 x 10^-23
2. 3.65 x 10^-23
3. 1.01 x 10^-23
4. 2.01 x 10^-23

Answer: (1) 7.31 x 10^-23

Question 30. 4.0 grams of caustic soda contain 

1. 6.023 x 10²³ atoms of hydrogen
2. 4 g atoms of sodium
3. 6.023 x 10²²atoms of sodium
4. 4 moles of caustic soda

Answer: (3) 6.023 x 10²² atoms of sodium:

WBBSE Class 9 Physical Science Avogadro’s number MCQs

Question 31. Which of the following weighs the least?

1. 24 g of magnesium
2. 0.9 moles of nitric oxide
3. 22.4 lit of N₂
4. 6.023 x 10²⁴ molecules of oxygen

Answer: (1) 24 g of magnesium

Question 32. One mole of CO₂ contains

1. 6.023 x 10²³ atoms of carbon
2. 6.023 x 10²³ atoms of oxygen
3. 18.1 x 10²³ molecules of carbon dioxide
4. 3 gram atoms of carbon dioxide

Answer: (1) 6.023 x 10²³  atoms of carbon

Question 33. One a.m.u. is

1. 1.00748 g
2. 0.000549 g
3. 1.66 x.10^-24 g
4. 6.023 x 10^-23 g

Answer:  (3) 1.66 x 10^-24g

Question 34. The vapour density of a gas is 11.2. The volume occupied by 11.2 g of the gas at NTP is

1. 1 L
2. 11.2 L
3. 22.4 L
4. 10 L

Answer: (2) 11.2 L

Question 35. The vapour density of pure ozone would be 

1. 16
2. 24
3. 32
4. 48

Answer: (2) 24

Question 36. At STP 5.6 lit of a gas weights 60 g. The vapour density of the gas is.

1. 30
2. 60
3. 120
4. 240

Answer: (3) 120

Question 37. The largest number of molecules is in 

1.  34 g water
2. 54 g of CO₂
3. 46 g of CH₃OH
4. 54 g of N₂ O₅

Answer : (1) 34 g water

Question 38. The number of oxygen atoms in 4.4 g of CO, is approximately 

1. 1.2 x 10²³
2. 6 x 10²³
3. 6 x10²²
4. 12 x 10²³

Answer:  (1) 1.2 x 10

Question 39. The number of molecules in 16 g of methane (CH,) is 

1. 3.0 x 10²³
2. 6.023 x 10²³
3. \(\frac{16}{6.023} \times 10^{23}\)
4. \(\frac{16}{3} \times 10^{23}\)

Answer. (2) 6.023 x 10²³

Question 40. If 0.56 g of a gas occupies 280 ml at NTP, then its molecular mass is 

1. 4.8
2.  44.8
3. 2
4. 22.4

Answer: (2) 44.8