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. What is the direction of current in a galvanic cell?
[A] same as the direction of electrons
[B] opposite to the direction of electrons
[C] Cant be determined
[D] None of the above
Show Answer
Correct Answer: B [opposite to the direction of electrons]
Notes:
As the switch in the galvanic cell is in the on position, the electrons flow from negative electrode to positive electrode. The direction of current flow is opposite to that of electron flow.
52. What do we call the cell potential when no current is drawn through the galvanic cell?
[A] Zero potential
[B] E.M.F
[C] Equilibrium potential
[D] None of the above
Show Answer
Correct Answer: B [E.M.F]
Notes:
The cell potential is called the cell electromotive force (emf) of the cell when no current is drawn through the cell. Also, It is now an accepted convention that we keep the anode on the left and the cathode on the right while representing the galvanic cell.
53. What do we call the molar conductivity when the concentration approaches zero?
[A] Reacting molar conductivity
[B] Zero level molar conductivity
[C] Limiting molar conductivity
[D] Ideal molar conductivity
Show Answer
Correct Answer: C [Limiting molar conductivity]
Notes:
When concentration approaches zero, the molar conductivity is known as limiting molar conductivity.
54. Which of the following is not a weak electrolyte?
[A] Acetic acid
[B] Carbonic acid
[C] Potassium Hydroxide
[D] All of the above
Show Answer
Correct Answer: C [Potassium Hydroxide]
Notes:
An electrolyte that does not completely dissociate in aqueous solution is known as weak electrolyte. For example: acetic acid, carbonic acid etc. Potassium Hydroxide is a strong electrolyte.
55. What happens to the molar conductivity of a weak electrolyte in case of dilution?
[A] No change
[B] increases slowly
[C] increases steeply
[D] decreases slowly
Show Answer
Correct Answer: C [increases steeply]
Notes:
In case of weak electrolyte, molar conductivity increases steeply on dilution, especially near lower concentrations. The weak electrolytes have lower degree of dissociation at higher concentrations.
56. Which of these is also known as isobutane?
[A] 2-Methylpropane
[B] 1-Methylpropane
[C] 3-Methylpropane
[D] Butane
Show Answer
Correct Answer: A [2-Methylpropane]
Notes:
isobutane is commonly known as 2-Methylpropane. Butane is commonly known as n-butane. Four carbon atoms of C4H10 can be joined either as Butane or 2-Methylpropane.
57. Which of the following is formed when an acid reacts with an alcohol?
[A] Ketones
[B] Esters
[C] Aldehydes
[D] Alkynes
Show Answer
Correct Answer: B [Esters]
Notes:
Esters are most commonly formed by reaction of an acid and an alcohol. Ethanoic acid reacts with absolute ethanol in the presence of an acid catalyst to give an ester.
58. Choose the correct statement about Oxalic acid:
[A] It is weaker than acetic acid
[B] Its condensed chemical formula is HOOCCOOH
[C] Both a and b
[D] None
Show Answer
Correct Answer: B [Its condensed chemical formula is HOOCCOOH]
Notes:
Oxalic acid is an organic compound with the formula C2H2O4. Its condensed formula is HOOCCOOH. Its acid strength is much greater than that of acetic acid.
59. What do we get when we pass phenol vapours over zinc dust?
[A] Methane
[B] Ethene
[C] Toluene
[D] Benzene
Show Answer
Correct Answer: D [Benzene]
Notes:
Phenol is reduced to benzene by passing its vapours over heated zinc dust. It is one of the methods of preparation of Benzene in laboratory.
60. Which of these alkanes has higher boiling point?
[A] Butane
[B] Methane
[C] Ethane
[D] Hexane
Show Answer
Correct Answer: D [Hexane]
Notes:
There is a steady increase in boiling point with the increase in molecular mass. This is due to the fact that the intermolecular van der Waals forces increase with increase of the molecular size or the surface area of the molecule.
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