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
Atomic Mass
= 28
14
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
Density
= 32
1.429
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.
Atom
|
Molecule
|
1. Atom is an non bonded entity.
|
1. Molecule is a bonded entity.
|
2. It may or may not exist freely.
Eg: CI
|
2. It can exist freely.
Eg: CI₂
|
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] + 1[16] = 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
6.023
×1023
= 0.5 moles
7. ________ have equal number of neutrons.
a. Isobars
b. Isotones
c. Isotopes
d. Mass Numbers
Answer: b. Isotones
8. Classify the following based on atomicity:
a. Chlorine
b. Neon
c. Phosphorous
d. Ozone
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.