Chemistry MCQs
Chemistry Objective (Multiple Choice) General Knowledge Questions & Answers for SSC-CGL, UPPSC, UPSC, NDA, CDS and UPSC Civil Services Prelims Examination.
1. Which among the following is the correct set of chemical formulae of Chile Saltpetre, Saltpetre and Quick Lime?
[A] KNO3, NaNO3, CaO
[B] NaNO3, KNO3, Ca(OH)2
[C] Na(OH)2, KOH, CaO
[D] NaNO3, KNO3, CaO
Show Answer
Correct Answer: D [NaNO3, KNO3, CaO]
Notes:
Saltpetre, also spelled Saltpeter, also called Nitre, or Niter, any of three naturally occurring nitrates, distinguished as (1) ordinary saltpetre, or potassium nitrate, KNO3; (2) Chile saltpetre, cubic nitre, or sodium nitrate, NaNO3; and (3) lime saltpetre, wall saltpetre, or calcium nitrate, Ca(NO3)2.
Calcium oxide (CaO), commonly known as quicklime or burnt lime, is a widely used chemical compound.
2. Which among the following is the objective of the Methyl tert-butyl ether (MTBE) mixing with Petroleum?
[A] Raise Octane Number
[B] Antioxidant Stabilizer
[C] Lead Scavanger
[D] Fuel Dye
Show Answer
Correct Answer: A [Raise Octane Number ]
Notes:
MTBE is a gasoline additive, used as an oxygenate to raise the octane number. Its use is controversial in the US and declining in that country in part because of its occurrence in groundwater and legislation favoring ethanol.
3. The primary part of Liquefied Petroleum Gas LPG is ______?
[A] Butane
[B] Methane
[C] Propane
[D] Butane or Propane
Show Answer
Correct Answer: D [Butane or Propane]
Notes:
LPG consists mainly of propane, propylene, butane, and butylene in various mixtures. The primary gas can be either Propane or Butane.
4. Which among the following was the first artificially produced element?
[A] Neptunium
[B] Ununbium
[C] Technetium
[D] none of the above
Show Answer
Correct Answer: C [Technetium]
Notes:
Technetium was the first artificially produced element. It was isolated by Carlo Perrier and Emilio Segrè in 1937. Technetium was created by bombarding molybdenum atoms with deuterons that had been accelerated by a device called a cyclotron.
5. Which of the following is emitted in Beta-decay process?
[A] Electron
[B] Positron
[C] Both a and b
[D] None
Show Answer
Correct Answer: C [Both a and b]
Notes:
In beta decay, a nucleus spontaneously emits an electron (βdecay) or a positron (β+decay). One can never predict which nucleus will undergo decay.
6. When is the gamma ray emitted?
[A] When a nucleus in a ground state goes to the excited state
[B] When a nucleus in an excited state spontaneously decays to its ground state
[C] When alpha rays and beta rays collide
[D] None of the above
Show Answer
Correct Answer: B [When a nucleus in an excited state spontaneously decays to its ground state]
Notes:
When a nucleus in an excited state spontaneously decays to its ground state (or to a lower energy state), a photon is emitted with energy equal to the difference in the two energy levels of the nucleus. This is the so-called gamma decay.
7. Which of the following is the balance equation for Aluminium + Copper chloride – Aluminium chloride + Copper?
[A] 2Al + 2CuCl3 – 2AlCl3 + Cu
[B] Al + 2CuCl2 – AlCl3 + 2Cu
[C] 2Al + 3CuCl2 – 2AlCl3 + 3Cu
[D] None of the above
Show Answer
Correct Answer: C [2Al + 3CuCl2 – 2AlCl3 + 3Cu]
Notes:
2Al + 3CuCl2 – 2AlCl3 + 3Cu is the balanced equation of Aluminium + Copper chloride – Aluminium chloride + Copper.
8. Which of the following group of elements contain the noble gases?
[A] s-block
[B] p-block
[C] d-block
[D] f-block
Show Answer
Correct Answer: B [p-block]
Notes:
The p-Block Elements comprise those belonging to Group 13 to 18 and these together with the s-Block Elements are called the Representative Elements or Main Group Elements. The 18th group i.e. the last group of the p-block elements is the noble gases group.
9. 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.
10. What is the effect of increase in concentration on the Molar conductivity?
[A] It increases
[B] It decreases
[C] It remains constant
[D] None of the above
Show Answer
Correct Answer: B [It decreases]
Notes:
Molar conductivity increases with decrease in concentration and decreases with increase in concentration. This is because the total volume of solution containing one mole of electrolyte also increases as the concentration decreases.
