1. From the given examples, form the pair of isotopes and the pair of isobars: 18Ar40, 17CI35, 20Ca40, 17CI37
Answer: Isotopes : 17CI35, 17CI37
Isobars : 18Ar40, 20Ca40
2. Molecular mass of Nitrogen is 28. Its atomic mass is 14. Find the atomicity of Nitrogen. (SEP - 2014, APRIL – 2014, 12)
Answer: Atomicity = Molecular Mass
Atomicity = 2
3. Gram molecular mass of oxygen is 32g/ Density of Oxygen is 1.42g/cc. Find the gram molecular volume of Oxygen.
Gram Molecular Volume = Gram Molar Mass
Gram Molecular Volume of Oxygen = 22.4 litre
4. ‘Cl’ represents chlorine atom, ‘CI₂’ represents chlorine molecule. List our any two difference between atoms and molecules.
1. Atom is an non bonded entity.
1. Molecule is a bonded entity.
2. It may or may not exist freely.
2. It can exist freely.
5. Calculate the gram molecular mass of water from the values of gram atomic mass of hydrogen and of Oxygen. (APRIL – 2013,12)
Gram atomic mass of hydrogen = 1g
Gram atomic mass of oxygen = 16g
Answer: H₂O = 2[H] + 1[O]
Gram molecular mass of water = 2 + 1 = 2 + 16
Gram molecular mass of water = 18g
6. One mole of any substance contains 6.023 ×1023 particles.
If 3.0115 × 1023 particles are present in CO₂. Find the number of moles.
Number of moles = No. Of molecules
6.023 × 1023
= 3.0115 × 1023
= 0.5 moles
7. ________ have equal number of neutrons.
d. Mass Numbers
Answer: b. Isotones
8. Classify the following based on atomicity:
Answer: Chlorine - Diatomic Molecule
Neon - Monotonic Molecule
Phosphorous - Polyatomic Molecule
Ozone - Triatomic Molecule
9. Identify and correct the mistake in each of the following:
a. The molar volume of gas at STP is 22.4 cm₃.
b. 2 × R.M.M. = V.D
c. An atom cannot exist independently.
d. The ratio of atoms in a molecule may be integral or simple or may not be fixed.
d. H₂O is a homo atomic molecule.
Answer: a. The molar volume of gas at STP is 22.4 Litre.
b. 2 × V.D. = R.M.M.
c. An atom may or may not exist independently.
d. The ratio of atoms in a molecule are intergral and fixed.
d. H₂O is a Hetero atomic molecule.