Chemistry MCQs
Chemistry Objective (Multiple Choice) General Knowledge Questions & Answers for SSC-CGL, UPPSC, UPSC, NDA, CDS and UPSC Civil Services Prelims Examination.
11. 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.
12. Which of the following represents the cell potential?
[A] sum of the electrode potentials of the cathode and anode
[B] difference between the electrode potentials of the cathode and anode
[C] half of the sum of the electrode potentials of the cathode and anode
[D] twice the difference between the electrode potentials of the cathode and anode
Show Answer
Correct Answer: B [difference between the electrode potentials of the cathode and anode]
Notes:
The cell potential is the difference between the electrode potentials (reduction potentials) of the cathode and anode. It is measured in volts.
13. Choose the correct statement about corrosion:
[A] Corrosion of metals is an electrochemical phenomenon
[B] Bisphenol can be used to cover the metal surface to prevent corrosion
[C] Both a and b
[D] None
Show Answer
Correct Answer: C [Both a and b]
Notes:
One of the simplest methods of to prevent corrosion is to prevent the surface of the metallic object to come in contact with atmosphere. This can be achieved by covering the surface with paint or by some chemicals (e.g. bisphenol).
14. What is the reason for the presence of the vast number of organic compounds in nature?
[A] Carbon exists in free state
[B] Catenation property of carbon
[C] Low atomic mass of carbon
[D] None of the above
Show Answer
Correct Answer: B [Catenation property of carbon]
Notes:
Because of the catenation property of carbon, vast number of organic compounds are present in nature. Catenation refers to the linkage of atoms of the same element into longer chains.
15. What is the octane number of iso-octane?
[A] 1
[B] 0
[C] 100
[D] 200
Show Answer
Correct Answer: C [100]
Notes:
Octane number, also known as octane rating, are based on a scale on which iso-octane is 100, which means minimal knock, and heptane is 0. The higher the octane number, the more compression required for fuel ignition.
16. Which of these is not an addition polymer?
[A] PVC
[B] Nylon 66
[C] Polypropylene
[D] All of the above
Show Answer
Correct Answer: B [Nylon 66]
Notes:
A polymer formed by direct addition of repeated monomers without the elimination of any small molecule is called addition polymer. Examples are polyethene, polypropylene and polyvinyl chloride, etc.
17. Which of these polymers is produced by a condensation reaction between ethylene glycol and ortho-phthalic acid?
[A] Neoprene
[B] Teflon
[C] Poly ethelene glycol phthalate
[D] None of the above
Show Answer
Correct Answer: C [Poly ethelene glycol phthalate]
Notes:
Poly ethelene glycol phthalate which is obtained by a condensation reaction between ethylene glycol and ortho-phthalic acid.
18. Which of these chemicals is used to dissolve the soap to make a transparent soap?
[A] Ethanoic acid
[B] Ethanol
[C] Benzene
[D] Propylene
Show Answer
Correct Answer: B [Ethanol]
Notes:
Variations in soaps are made by using different raw materials. Transparent soaps are made by dissolving the soap in ethanol and then evaporating the excess solvent.
19. Why the bacteria cannot degrade the detergents easily?
[A] Due to its sticky nature
[B] Due to highly branched hydrocarbon chain
[C] Due to its heavy density
[D] None of the above
Show Answer
Correct Answer: B [Due to highly branched hydrocarbon chain]
Notes:
Main problem that appears in the use of detergents is that if their hydrocarbon chain is highly branched, then bacteria cannot degrade this easily.
20. Which of the following is the process to remove calcium and magnesium from hard water?
[A] Filtration
[B] Flocculation
[C] Sedimentation
[D] Water softening
Show Answer
Correct Answer: D [Water softening]
Notes:
Water softening is the removal of calcium, magnesium, and certain other metal cations in hard water. The resulting soft water requires less soap for the same cleaning effort, as soap is not wasted mopping up calcium ions.
