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. 2,4-D, which is sold as a weed killer of the broad-leaved weeds is a synthetic version of __:
[A] Auxin Hormone
[B] Cytokinin Hormone
[C] Xylitol
[D] None of them
Show Answer
Correct Answer: A [Auxin Hormone ]
Notes:
2,4-dichlorophenoxyacetic acid (2,4-dichlorophenoxyethanoic acid) is a synthetic auxin frequently used as a weed killer of broad-leaved weeds. When two herbicides 2,4,5-T and 2,4-D and mixed in equal parts, it is called Agent Orange, which was used by US in Vietnam war.
3. Which among the following is known as Quick Lime?
[A] CaO
[B] CaCO2
[C] Ca(OH)2
[D] CaCl2
Show Answer
Correct Answer: A [CaO]
Notes:
Calcium oxide (CaO), commonly known as quicklime or burnt lime, is a widely used chemical compound. It is a white, caustic, alkaline crystalline solid at room temperature.
4. Calamine is an ore of which among the following?
[A] Zinc
[B] Copper
[C] Mercury
[D] Iron
Show Answer
Correct Answer: A [Zinc]
Notes:
Calamine is an ore that contains zinc carbonate along with impurities like iron oxide. Through smelting, the zinc carbonate in calamine can be reduced to extract pure zinc metal. Other common zinc ores are sphalerite (zinc sulfide) and smithsonite (zinc carbonate). So calamine is considered a zinc ore due to its zinc carbonate content.
5. Under standard conditions, which of the following is the most stable form of carbon?
[A] Charcoal
[B] Graphite
[C] Diamond
[D] Amorphous Carbon
Show Answer
Correct Answer: B [Graphite]
Notes:
Under standard conditions, Graphite is the most stable form of carbon. It is commonly used in pencils and lubricants due to its layered structure. These layers can move over each other, making graphite soft and slippery. Besides Graphite, other forms of carbon are diamond, charcoal, and amorphous carbon, each with unique properties and applications.
6. Which of the following elements have a compound named as Hydrogen peroxide?
[A] Hydrogen, Carbon and Oxygen
[B] Hydrogen only
[C] Hydrogen and Oxygen
[D] Hydrogen, Oxygen and Potassium
Show Answer
Correct Answer: C [Hydrogen and Oxygen]
Notes:
Hydrogen peroxide is a compound of Hydrogen and Oxygen.
7. Which of the following compounds is manufactured using the Contact Process?
[A] Sulphuric Acid
[B] Nitric Acid
[C] Hydrochloric Acid
[D] Benzene
Show Answer
Correct Answer: A [Sulphuric Acid]
Notes:
The Contact Process is a method primarily used for preparing sulphuric acid on a large scale. It involves the oxidation of sulfur dioxide to sulfur trioxide in presence of a catalyst such as vanadium pentoxide. The subsequent hydration of sulfur trioxide produces sulphuric acid. The Contact Process allows the production of high concentrations of sulphuric acid under economically feasible conditions.
8. Which of the following defines the solubility of a solution?
[A] amount of the solvent present in the saturated solution
[B] amount of the solute present in the saturated solution
[C] amount of the solute per amount of solute in the solution
[D] difference of amount of solvent and the amount of solute
Show Answer
Correct Answer: B [amount of the solute present in the saturated solution]
Notes:
The amount of the solute present in the saturated solution at a given temperature is called its solubility.
9. Which of the following does not represent the Atomic number of an atom?
[A] number of protons in the nucleus of an atom
[B] number of electrons in a neutral atom
[C] number of neutrons in the nucleus of an atom
[D] None of the above
Show Answer
Correct Answer: C [number of neutrons in the nucleus of an atom]
Notes:
The number of protons present in the nucleus of an atom or the number of electrons in a neutral atom is equal to its atomic number. It is represented by Z.
10. 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.
