Chemistry Multiple Choice Questions on “Mole Concept and Molar Masses”.
1. According to S.I. the system, ______ was used to measure the amount of substance.
a) mole
b) weight machine
c) weight
d) mass
Answer: a
Clarification: One mole is the amount of a substance that contains as many particles as there are atoms in exactly 12 g of the carbon atom. So S.I. the system took mole as the seventh base fundamental quantity (symbol = mol).
2. What’s the number of entities or particles together in mole concept known as?
a) Boltzmann constant
b) Avogadro’s number
c) Universal gas constant
d) Reynold’s number
Answer: b
Clarification: Avogadro number denoted by NA. Its value is 602213670000000000000000, also written as 6.022×1023. It’s the number of entities in 1 mol of a substance. The units may be electrons, atoms, ions, or molecules, depending on the nature of the substance.
3. 1 u = Ma/NA.
a) True
b) False
Answer: a
Clarification: In the above given equation 1 u = Mu/NA; “u” refers to the atomic mass unit, Mu refers to molar mass constant(Its value is defined to be 1 g/mol in SI units). 1 u = Ma/NA = 1.660539040 x 10-27 kg. Hence the above statement is true.
4. A mole of any substance contains _______
a) 6.022 x 1026 particles
b) 6.022 x 1022 particles
c) 6.022 x 1023 particles
d) 3.022 x 1022 particles
Answer: c
Clarification: The answer is Avogadro’s number. One mole of any substance contains Avogadro’s number of particles. Avogadro number denoted by NA. Its value is 602213670000000000000000, also written as 6.022×1023.
5. 12.044 x 1023 atoms of oxygen contains _______
a) 1 mole of oxygen
b) 2 moles of oxygen
c) 3 moles of oxygen
d) 4 moles of oxygen
Answer: b
Clarification: One mole of any substance contains Avogadro’s number of particles. Its value is 6.022×1023 atoms. But here it’s given 12.044 x 1023 atoms, thereby dividing it by Avogadro’s number; 12.044 x 1023 atoms/6.022×1023 atoms = 2 moles. Hence it contains 2 moles of oxygen.
6. If one mole of ammonia contains “y” number of particles, then how many particles do 1 mole of glucose contain?
a) 2y
b) 0.5y
c) 3y
d) y
Answer: d
Clarification: Let it be any compound, but one mole of a substance always contains Avogadro’s number of particles. In the above question, Avogadro’s number (6.022×1023) is given by the letter “y”. so, in 1 mole of glucose, there is y number of particles.
7. What’s the number of particles in 10 moles of hydrochloric acid?
a) 6.022 x 1022 particles
b) 6.022 x 1023 particles
c) 6.22 x 1023 particles
d) 3.22 x 1022 particles
Answer: a
Clarification: One mole of any substance contains Avogadro’s number of particles. Its value is 6.022×1023 atoms. But here the question is about 10 moles of a substance. So multiply the Avogadro’s number by 10. Therefore 6.022×1023 x 10 = 6.022×1022.
8. Which of the following statement is correct?
a) The value of Avogadro’s number is 6.022×1022 atoms
b) One molecule of any substance contains Avogadro’s number of particles
c) One mole is the amount of a substance that contains as many particles as there are atoms in exactly 12 g of the carbon atom
d) 1 u is not equal to Ma/NA
Answer: c
Clarification: The corrected statements are as follows: the value of Avogadro’s number is 6.022×1023 atoms, one molecule of any substance contains Avogadro’s number of particles & 1 u = Ma/NA. The correct option is that one mole is the amount of a substance that contains as many particles as there are atoms in exactly 12 g of the carbon atom.
9. One mole of sucrose contains how many grams of sucrose?
a) 342g
b) 343g
c) 341g
d) 340g
Answer: a
Clarification: One mole of sucrose is C12H22O11 The individual mass of carbon is 12 amu, the individual mass of hydrogen is 1 amu & the individual mass of oxygen is 16 amu. But sucrose has 12 carbons, 22 hydrogens and 11 oxygens, that is 12 x 12 + 22 x 1 + 11 x 16 = 342g.
10. 1 mole of ammonia is of 17 g. Then what is the mass of 0.3 moles of ammonia?
a) 21g
b) 2.1g
c) 17g
d) 1g
Answer: b
Clarification: Given that, 1 mole of ammonia is of 17 g. 0.3 mole of ammonia contains 17 x 0.3g of mass. IT’s because the molecular weight of a given pcompound is directly proportional to the number of moles of the given compound.