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 the following quantum numbers is represented by a period of the modern periodic table?
[A] Principal quantum number
[B] Azimuthal quantum number
[C] Magnetic quantum number
[D] None of the above
Show Answer
Correct Answer: A [Principal quantum number]
Notes:
The Period in the modern periodic table indicates the value of ‘n’ (principal quantum number) for the outermost or valence shell.
52. 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
53. Which is the first element in the Actinoid series?
[A] Actinium
[B] Bohrium
[C] Mendelevium
[D] Nobelium
Show Answer
Correct Answer: A [Actinium]
Notes:
The actinoid series comprises of the 15 metallic chemical elements with atomic numbers from 89 to 103 starting from actinium through lawrencium.
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 we call the amount of energy required to break one mole of bonds of a particular type between two atoms in a gaseous state?
[A] Ionisation Potential
[B] Bond Enthalpy
[C] Electron affinity
[D] Bond order
Show Answer
Correct Answer: B [Bond Enthalpy]
Notes:
Bond Enthalpy is the amount of energy required to break one mole of bonds of a particular type between two atoms in a gaseous state. Its unit is KJ-1.
56. 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.
57. What is the molecular geometry of a Methane molecule?
[A] Linear
[B] Trigonol Planar
[C] Tetrahedral
[D] Trigonol bipyramidal
Show Answer
Correct Answer: C [Tetrahedral]
Notes:
The hydrogen atoms sharing electrons with the central carbon atom have a 109 degree bond angle giving the molecule a tetrahedral geometry.
58. Choose the correct statement about Litmus solution:
[A] Its colour is brown
[B] It is slightly acidic in nature
[C] It is extracted from lichen
[D] All of the above
Show Answer
Correct Answer: C [It is extracted from lichen]
Notes:
Litmus solution is purple in colour. It is neither acidic nor basic in nature. It is extracted from lichen, a plant belonging to the division Thallophyta, and is commonly used as an indicator.
59. Choose the incorrect acid-source pair?
[A] Citric acid – Lemon
[B] Lactic acid – Sour milk
[C] Oxalic acid – Ant sting
[D] Methanoic acid – Nettle sting
Show Answer
Correct Answer: C [Oxalic acid – Ant sting]
Notes:
An ant sting contains Methanoic acid. The sting leaves an acid which causes irritation. Use of a mild base like baking soda on the stung area gives relief.
60. What do we call the number of water molecules present in one formula unit of a salt?
[A] Formula number of salt
[B] Power of the salt
[C] Water of crystallisation
[D] Hydro number
Show Answer
Correct Answer: C [Water of crystallisation]
Notes:
The fixed number of water molecules present in one formula unit of a salt is called water of crystallisation. For example, one formula unit of copper sulphate has five molecules of water in it.
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