Chemistry MCQs
Chemistry Objective (Multiple Choice) General Knowledge Questions & Answers for SSC-CGL, UPPSC, UPSC, NDA, CDS and UPSC Civil Services Prelims Examination.
11. What do we call the process that separates a pure solid in the form of its crystals from a solution?
[A] Crystallisation
[B] Sublimation
[C] Chromatography
[D] Distillation
Show Answer
Correct Answer: A [Crystallisation]
Notes:
Crystallisation is a process that separates a pure solid in the form of its crystals from a solution. For example: purification of the salt obtained from sea water.
12. 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.
13. 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.
14. 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.
15. What is the pH of water in the Acid rain?
[A] More than 12
[B] Less than 5.5
[C] Between 7 and 11
[D] None of the above
Show Answer
Correct Answer: B [Less than 5.5]
Notes:
When pH of rain water is less than 5.5, it is called acid rain. When acid rain flows into the rivers, it lowers the pH of the river water. The survival of aquatic life in such rivers becomes difficult.
16. What is the Gibbs energy of a cell (nF=amount of charge passed, E= EMF of the cell)?
[A] -1/2nFE
[B] 2nFE
[C] -nFE
[D] nFE
Show Answer
Correct Answer: C [-nFE]
Notes:
If the emf of the cell is E and nF is the amount of charge passed and ∆rG is the Gibbs energy of the reaction, then Gibbs energy is equal to – nFE.
17. 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.
18. Which of the following is correct about a strong electrolyte?
[A] It is a good conductor of electricity
[B] Molar conductivity increases slowly with dilution
[C] Both a and b
[D] None
Show Answer
Correct Answer: C [Both a and b]
Notes:
The ions of strong electrolytes are good conductors of electricity in the solution. The Molar conductivity in case of strong electrolytes increases slowly with dilution.
19. 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.
20. Which of the following is true about an inert electrode?
[A] It does not participate in the chemical reaction
[B] It acts as a source or sink for electrons
[C] Both a and b
[D] None of the above
Show Answer
Correct Answer: C [Both a and b]
Notes:
An inert electrode does not participate in chemical reaction and acts as a source or sink for electrons. Example of an inert electrode: Platinum or gold electrode.
