51. What is the reason for the increase in the electronegativity across a period from left to right?
[A] attraction between the valence electrons and the nucleus increases
[B] attraction between the valence electrons and the nucleus decreases
[C] increase in the atomic weight
[D] None of the above
Show Answer
Correct Answer: A [attraction between the valence electrons and the nucleus increases]
Notes:
The attraction between the outer (or valence) electrons and the nucleus increases as the atomic radius decreases in a period. The electronegativity also increases.
52. In which of the following groups is Gold placed in the modern periodic table?
[A] 10
[B] 12
[C] 11
[D] 9
Show Answer
Correct Answer: C [11]
Notes:
Group 11 of the modern periodic table is a group of chemical elements in the periodic table, consisting of copper (Cu), silver (Ag), and gold (Au).
53. The Lanthanoids are part of which of the following block of elements in the periodic table?
[A] p-block
[B] s-block
[C] d-block
[D] f-block
Show Answer
Correct Answer: D [f-block]
Notes:
Lanthanoids form part of the series of chemical elements comprising the 15 metallic chemical elements with atomic numbers 57 through 71, from lanthanum through lutetium. They are a part of f-block of elements in the periodic table
54. Which of the following is true about a water molecule?
[A] It has a bent-shaped structure
[B] The bond angle is 120°
[C] It is a non-polar solvent
[D] All of the above
Show Answer
Correct Answer: A [It has a bent-shaped structure]
Notes:
The water molecule has a bent-shaped structure. The bond angle is 104.5° and it is a polar solvent. Infact, water is known as a universal solvent.
55. What is the reason for different molecular arrangements as per VSEPR theory?
[A] To minimize mutual repulsion
[B] To minimize mutual attraction
[C] To minimize surface tension
[D] To have the minimum area
Show Answer
Correct Answer: A [To minimize mutual repulsion]
Notes:
As per the Valence Shell Electron Pair Repulsion (VSEPR) theory, the electron pairs (both bonding and non-bonding) around the central atom in a molecule arrange themselves in space in such a way that they minimize their mutual repulsion.
56. In which of the following pairs is the repulsion greatest as per the VSEPR Theory?
[A] lone pair – lone pair
[B] lone pair – bond pair
[C] bond pair – bond pair
[D] Same for all
Show Answer
Correct Answer: A [lone pair – lone pair]
Notes:
The repulsion of a lone pair of electrons for another lone pair is greater than that between a bond pair and a lone pair which in turn is greater than that between two bond pairs. The correct order of repulsive force is as: lone pair – lone pair > lone pair – bond pair > bond pair – bond pair.
57. What is the bond angle in case of Ammonia molecule?
[A] 120°
[B] 150°
[C] 66°
[D] 107°
Show Answer
Correct Answer: D [107°]
Notes:
The bond angle in case of Ammonia molecule is 107° and the molecular geometry is trigonal pyramidal. The number of bond pairs in Ammonia is 3 and lone pair is 1.
58. Which of the following represents the bond order in Molecular orbital theory?
[A] half the difference between the number of bonding and antibonding electrons
[B] twice the difference between the number of bonding and antibonding electrons
[C] the difference between the number of bonding and antibonding electrons
[D] the sum of the number of bonding and antibonding electrons
Show Answer
Correct Answer: A [half the difference between the number of bonding and antibonding electrons]
Notes:
The bond order in Molecular orbital theory is given by half the difference between the number of bonding and antibonding electrons.
59. Which of the following molecules have an electrovalent bonding?
[A] NaCl
[B] MgO
[C] NH3
[D] Both a and b
Show Answer
Correct Answer: D [Both a and b]
Notes:
Both NaCl and MgO are an electrovalent compound formed by the complete transfer of electrons from one atom to another. NH3 is a covalent compound.
60. What is the bond order in O2 molecule?
[A] 1
[B] 2
[C] 3
[D] 4
Show Answer
Correct Answer: B [2]
Notes:
The Bond Order is given by the number of bonds between the two atoms in a molecule. The bond order O2 molecule is 2 as they share two electrons.
