Chemistry MCQs
Chemistry Objective (Multiple Choice) General Knowledge Questions & Answers for SSC-CGL, UPPSC, UPSC, NDA, CDS and UPSC Civil Services Prelims Examination.
1. The easily noticed smell of the LPG gas is because of which among the following?
[A] Butane
[B] Propane
[C] Methane
[D] Ethanethiol
Show Answer
Correct Answer: D [Ethanethiol]
Notes:
Ethanethiol or stench, is a organosulfur compound and is used to add to the otherwise odorless gaseous products such as liquefied petroleum gas (LPG) to help warn of gas leaks.
2. Which of the following type of Coal has maximum carbon content?
[A] Peat
[B] Lignite
[C] Antharacite
[D] Bituminious
Show Answer
Correct Answer: C [Antharacite]
Notes:
Anthracite, often referred to as hard coal, is a hard, compact variety of coal that has a submetallic luster. It has the highest carbon content, the fewest impurities, and the highest energy density of all types of coal and is the highest ranking of coals.
3. Kazimierz Funk or Casimir Funk, was a Polish biochemist, generally credited with the first formulation of the concept of which of the following ?
[A] Amino Acids
[B] DNA
[C] RNA
[D] Vitamins
Show Answer
Correct Answer: D [Vitamins]
Notes:
Kazimierz Funk (1884 – 1967) was a Polish biochemist, and one of the first to formulate the concept of Vitamins.
4. Which among the following is the most important characteristic of Noble metals?
[A] Luster
[B] Non reactive nature
[C] Preciousness
[D] Rare availability
Show Answer
Correct Answer: B [Non reactive nature]
Notes:
Noble metals, such as gold, silver, and platinum, are primarily characterized by their non-reactive nature. This means they resist oxidation and corrosion, making them ideal for use in jewelry and electronics. Unlike base metals, noble metals do not easily form compounds with other elements, which is why they maintain their luster and appearance over time. Their rarity and preciousness are secondary characteristics, but their chemical stability is what truly defines them as noble.
5. 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.
6. What is the reason that despite being third most abundant element on the Earth’s surface and most abundant chemical substance in the universe, Hydrogen is not found as a gas in Earth’s atmosphere?
[A] It is very reactive and unstable gas
[B] It is so light that readily escapes earth’s gravity
[C] It is not found in free state in nature
[D] None of the above reasons
Show Answer
Correct Answer: B [ It is so light that readily escapes earth’s gravity]
Notes:
Under ordinary conditions on Earth, elemental hydrogen exists as the diatomic gas, H2. However, hydrogen gas is very rare in the Earth’s atmosphere (1 ppm by volume) because of its light weight, which enables it to escape from Earth’s gravity more easily than heavier gases. However, hydrogen is the third most abundant element on the Earth’s surface, mostly in the form of chemical compounds such as hydrocarbons and water. Hydrogen gas is produced by some bacteria and algae and is a natural component of flatus, as is methane, itself a hydrogen source of increasing importance.
7. With reference to the Radioactivity, which among the following is called an isomeric transition?
[A] Alpha emission
[B] Gamma emission
[C] Beta emission
[D] X-Ray emission
Show Answer
Correct Answer: B [ Gamma emission]
Notes:
An isomeric transition is a radioactive decay process that involves emission of a gamma ray from an atom where the nucleus is in an excited metastable state, referred to in its excited state, as a nuclear isomer. The emission of a gamma ray from an excited nuclear state allows the nucleus to lose energy and reach either a lower energy state, sometimes its ground state. In certain cases, the excited nuclear state following a nuclear reaction or other type of radioactive decay, has a half live that is more than 100 to 1000 times longer than the average 10-12 seconds, and this excited state is referred to as a metastable nuclear excited state. Some nuclei are able to stay in this metastable excited state for minutes, hours, days, or occasionally far longer, before undergoing gamma decay, in which they undergo radioactive decay with primary emission of a gamma ray.
8. Which of the following is correct about ozone?
[A] it is a red coloured gas
[B] it is odourless
[C] it is harmless in small concentrations
[D] All of the above
Show Answer
Correct Answer: C [it is harmless in small concentrations]
Notes:
Pure ozone is a pale blue gas, dark blue liquid and violet-black solid. Ozone has a characteristic smell and in small concentrations it is harmless. However, if the concentration rises above about 100 parts per million, breathing becomes uncomfortable resulting in headache and nausea.
9. Which of the following metal is the main constituent in Pewter alloy?
[A] Lead
[B] Zinc
[C] Tin
[D] Iron
Show Answer
Correct Answer: C [Tin]
Notes:
The term pewter covers a variety of alloys consisting primarily of tin. It is composed of 85–99% tin, mixed with copper, antimony, bismuth, silver or lead..
10. What is Rose metal?
[A] It is an alloy of Nickel, Tin and Zinc
[B] It is an alloy of Bismuth, Copper and Palladium
[C] It is an alloy of Palladium, Tin and Lead
[D] It is an alloy of Bismuth, Tin and Lead
Show Answer
Correct Answer: D [It is an alloy of Bismuth, Tin and Lead]
Notes:
Rose metal is an alloy of Bismuth, Tin and Lead. It’s a fusible alloy with low melting point commonly used for soldering.