General Science Chemistry MCQs
Chemistry Objective (Multiple Choice) General Knowledge Questions & Answers for SSC-CGL, UPPSC, UPSC, NDA, CDS and UPSC Civil Services Prelims Examination
71. Which of these species will have the largest atomic size?
[A] Na
[B] Mg
[C] Mg2+
[D] K
Show Answer
Correct Answer: D [K]
Notes:
Atomic size increases down the group as new shells are added. Therefore, Potassium (K) will have the largest size among the given elements as it belongs to the 4th period where as other elements belong to 3rd period.
72. Which of the following molecules have a T-shape arrangement?
[A] Ozone
[B] Water
[C] Chlorine Trifluoride
[D] Sulphur dioxide
Show Answer
Correct Answer: C [Chlorine Trifluoride]
Notes:
Chlorine trifluoride has 10 electrons around the central chlorine atom. There are five electron pairs arranged in a trigonal bipyramidal shape and two equatorial lone pairs making the final structure T-shaped.
73. What do we call the covalent bond where the electrons of the shared pair are contributed by only one species?
[A] Polar Covalent bonds
[B] Coordination Covalent bonds
[C] Unilateral Covalent bonds
[D] None of the above
Show Answer
Correct Answer: B [Coordination Covalent bonds]
Notes:
The covalent bond where the electrons of the shared pair are contributed by only one species are called as Coordination Covalent bonds or Dative bonds. The common example is the formation of a bond between boron trifluoride (BF3) and ammonia (NH3).
74. Choose the correct statement:
[A] Water exists as liquid due to hydrogen bonding
[B] Hydrogen bond is a weak bond as compared to ionic bond
[C] Both a and b
[D] None of the above
Show Answer
Correct Answer: C [Both a and b]
Notes:
Hydrogen bond is a weak bond and is quite small as compared to the covalent bond. it is due to hydrogen bonding only that water exists as a liquid.
75. 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.
76. 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.
77. What is the relationship between bond energy and bond length?
[A] Bond energy is independent of bond length
[B] Bond energy increases with the increase of bond length
[C] Bond energy decreases with the increase of bond length
[D] None of the above
Show Answer
Correct Answer: C [Bond energy decreases with the increase of bond length]
Notes:
The general relationship between bond energy and bond length is that the bond energy decreases with the increase of bond length between two atoms.
78. What is the shape of SF4 molecule?
[A] Bent
[B] See-saw
[C] Trigonol Pyramidal
[D] T-shape
Show Answer
Correct Answer: B [See-saw]
Notes:
SF4 molecule is see-saw in shape. It has 4-bonding pairs of electrons and one lone pair of electrons.
79. What is the PH of human blood?
[A] 8.2
[B] 7.4
[C] 6.5
[D] 7
Show Answer
Correct Answer: B [7.4]
Notes:
Blood is normally slightly basic, with a normal pH range of 7.35 to 7.45. Usually the human body maintains the pH of blood close to 7.40.
80. What do we call the device which converts the chemical energy of a spontaneous redox reaction into electrical energy?
[A] Galvanic cell
[B] Fuel cell
[C] Electrolytic cell
[D] None of the above
Show Answer
Correct Answer: A [Galvanic cell]
Notes:
A galvanic cell is an electrochemical cell that converts the chemical energy of a spontaneous redox reaction into electrical energy. Daniel cell is a kind of Galvanic cell.
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