Chemistry MCQs
Chemistry Objective (Multiple Choice) General Knowledge Questions & Answers for SSC-CGL, UPPSC, UPSC, NDA, CDS and UPSC Civil Services Prelims Examination.
1. What happens to ozone’s volume when it is heated?
[A] Increases
[B] Decreases
[C] Remains unchanged
[D] First increases, then decreases
Show Answer
Correct Answer: A [Increases]
Notes:
According to Charles’s Law, for gases at constant pressure, volume increases with temperature. Heating ozone increases the kinetic energy of molecules, expanding its volume if pressure is constant. Ozone (O₃) behaves like other gases, expanding when heated. This law applies to all ideal gases and ozone approximates ideal behavior under moderate conditions.
2. Which acid is described as HOOCCOOH?
[A] Oxalic Acid
[B] Acetic Acid
[C] Carbonic Acid
[D] Citric Acid
Show Answer
Correct Answer: A [Oxalic Acid]
Notes:
Oxalic acid is an organic compound with the formula C₂H₂O₄. Some call it “crab acid” due to its appearance. Its condensed formula is HOOCCOOH, reflecting its classification as the simplest dicarboxylic acid.
3. 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.
4. What is the primary use of Phenolphthalein in chemistry?
[A] A Solvent
[B] A Dye
[C] A Catalyst
[D] A Detergent
Show Answer
Correct Answer: B [A Dye]
Notes:
Phenolphthalein is commonly employed as a pH indicator in titrations due to its distinct color change in varying pH levels. At pH 8.2, it appears colorless but turns pink as the pH increases to 10. It is not used as a solvent, catalyst or detergent. It also finds applications in forensic science for detecting latent blood stains.
5. Consider the following:
- Copper
- Zinc
- Tin
Gun Metal is the alloy of which among the above?
[A] 1 & 2
[B] 1 & 3
[C] 2 & 3
[D] 1, 2 & 3
Show Answer
Correct Answer: D [1, 2 & 3]
Notes:
Gun metal is an alloy primarily composed of copper, tin, and zinc. Specifically, it typically contains about 88% copper, 10% tin, and 2% zinc. This alloy is known for its strength, corrosion resistance, and ability to withstand high temperatures, making it ideal for manufacturing firearms and artillery. The term “gun metal” dates back to the 15th century when it was used for cannons and other weaponry.
6. In a photochemical smog, which gas causes irritation to mucous membrane and respiratory system?
[A] Nitrous oxide
[B] Sulphur dioxide
[C] Ozone
[D] Carbon monoxide
Show Answer
Correct Answer: C [ Ozone]
Notes:Ozone (O3) is the most common photochemical oxidant in photochemical smog. Inhaling ozone can cause irritation to the mucous membrane and respiratory system. Ozone can also cause chest constriction and damage to vegetation.
Other components of photochemical smog include:
- Nitrogen dioxide (NO2)
- Peroxyacetylnitrate (PAN)
- Aldehydes
Other air pollutants that can be harmful to humans include:
- Sulfur dioxide
- Volatile organic compounds (VOCs)
- Dioxins
- Polycyclic aromatic hydrocarbons (PAHs)
Carbon monoxide can cause hyperventilation, respiratory distress, and stillbirths. At high levels, carbon monoxide can even cause direct poisoning.
7. Which of the following chemicals is also known as "sweet oil of vitriol"?
[A] Diethyl ether
[B] Aluminium sulphate
[C] Sulphuric acid
[D] Iron(III) sulphate
Show Answer
Correct Answer: A [ Diethyl ether]
Notes:
Diethyl ether is a colourless, highly volatile & flammable organic compound. It was earlier used for anaesthesia but after the development of non-flammable drugs, its uses as anaesthetic has been reduced.
8. Which of the following is correct about the atomic and ionic radii of the alkaline earth metals?
[A] it is smaller than corresponding alkali metals in the same periods
[B] it is larger than corresponding alkali metals in the same periods
[C] It is same as the corresponding alkali metals in the same periods
[D] None of the above
Show Answer
Correct Answer: A [it is smaller than corresponding alkali metals in the same periods]
Notes:
The atomic and ionic radii of the alkaline earth metals are smaller than corresponding alkali metals in the same periods due to the increased nuclear charge in these elements.
9. Which of these is NOT an allotropic form of carbon?
[A] Diamond
[B] Graphite
[C] Fullerene
[D] None of the above
Show Answer
Correct Answer: D [None of the above]
Notes:
Carbon exhibits many allotropic forms; both crystalline as well as amorphous. Diamond and graphite are two well-known crystalline forms of carbon. In 1985, third form of carbon known as fullerenes was discovered.
10. Which of the following is NOT correct about Sodium chloride?
[A] It is a covalent compound
[B] It is also known as common salt
[C] It is also used in de-icing of roadways during snowfall
[D] It is used as a food preservative
Show Answer
Correct Answer: A [It is a covalent compound]
Notes:
Sodium chloride (NaCl) is used as a common salt or table salt for domestic purpose and used as a food preservative. It is an ionic compound. It is also used in de-icing of roadways during snowfall.
