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
51. Which of these methods can be used to prevent rancidity?
[A] Adding antioxidants to the food
[B] Storing food at low temperature
[C] Replace the air with nitrogen in the packing material
[D] All of the above
Show Answer
Correct Answer: D [All of the above]
Notes:
When food containing fats and oils are exposed to the atmosphere, the oxidation of fat and oil occurs, this is called as Rancidity.
52. Which of the following is correct about Mendeleev’s Periodic Table?
[A] Argon is placed before Potassium
[B] Cobalt is placed before Nickel
[C] Tellurium is placed before iodine
[D] All of the above
Show Answer
Correct Answer: D [All of the above]
Notes:
All statements represent the anomalous pairs of elements in Mendeleev’s Periodic Table. The atomic mass of argon is 39.9 and that of potassium 39.1. But argon is placed before potassium in the periodic table. Similarly, Tellurium is placed before iodine and Cobalt is placed before Nickel.
53. Choose the correct statement about the modern periodic table:
[A] Elements in any one group contain the same number of valence electrons
[B] Elements in any one period contain the same number of shells
[C] Both a and b
[D] None
Show Answer
Correct Answer: C [Both a and b]
Notes:
Elements present in any one group of the modern periodic table have the same number of valence electrons. Elements in any one period contain the same number of shells.
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 do the dots represent in the Lewis dot structures?
[A] positrons
[B] electrons
[C] atoms
[D] neutrons
Show Answer
Correct Answer: B [electrons]
Notes:
The dots in the Lewis dot structure represent electrons. Lewis introduced theses simple notations to represent valence electrons in an atom.
56. Which of the following hydrogen bond is formed in the case of o-nitrophenol?
[A] Intramolecular
[B] Intermolecular
[C] Both a and b
[D] None
Show Answer
Correct Answer: B [Intermolecular]
Notes:
Intermolecular Hydrogen bond is formed when hydrogen atom is in between the two highly electronegative atoms present within the same molecule. For example: hydrogen is in between two Oxygen atom in the case of o-nitrophenol.
57. 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.
58. What is the length of O-O double bond in an ozone molecule?
[A] 121 pm
[B] 148 pm
[C] 143 pm
[D] 123 pm
Show Answer
Correct Answer: A [121 pm]
Notes:
the length of O=O double bond in an ozone molecule is 121 pm and the length of O-O single bond in an ozone molecule is 148 pm.
59. What is the dipole moment in BF3 molecule?
[A] 0
[B] 1
[C] 1.85
[D] 6.22
Show Answer
Correct Answer: 0 []
Notes:
The dipole moment in BF3 molecule is 0 because the two equal bond dipoles point in opposite directions and cancel the effect of each other.
60. 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.
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