Chemistry MCQs
Chemistry Objective (Multiple Choice) General Knowledge Questions & Answers for SSC-CGL, UPPSC, UPSC, NDA, CDS and UPSC Civil Services Prelims Examination.
1. Presence of which among the following minerals in Banana makes them slightly radioactive?
[A] Sodium
[B] Calcium
[C] Magnesium
[D] Pottasium
Show Answer
Correct Answer: D [Pottasium]
Notes:
Bananas contain potassium-40, a radioactive isotope of potassium, which makes them slightly radioactive. The radiation is very minor and not dangerous at all to humans, but it is enough to trigger sensitive radiation sensors. The potassium provides bananas some of their nutritional benefits as well.
2. Which acid is described as HOOCCOOH?
[A] Oxalic Acid
[B] Acetic Acid
[C] Carbonic Acid
[D] Citric Acid
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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 of the following type of Coal has maximum carbon content?
[A] Peat
[B] Lignite
[C] Antharacite
[D] Bituminious
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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.
4. What is the number of naturally occurring Halogens in the periodic table?
[A] 3
[B] 4
[C] 5
[D] 6
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Correct Answer: C [5]
Notes:
fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At)
5. Which among the following allotropes of Oxygen is found in 6 phases under various pressures and temperatures?
[A] Ozone
[B] Tetra oxygen
[C] Octaoxygen
[D] None of them
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Correct Answer: C [Octaoxygen]
Notes:
The correct answer is Octaoxygen. Octaoxygen (O8) is an allotrope of oxygen that can exist in multiple phases under varying pressures and temperatures. It was first synthesized in 2001 and is notable for its unique molecular structure, which consists of eight oxygen atoms. Ozone (O3) is well-known but does not exhibit multiple phases like octaoxygen. Tetraoxygen (O4) is less stable and not commonly referenced in the same context.
6. Sodium bicarbonate decomposes above 70 °C, making it usable in bakery products. What end product of this thermal decomposition process contributes to its use in baking?
[A] Hydrogen
[B] Carbon Dioxide
[C] Water Vapor
[D] Sodium Carbonate
Show Answer
Correct Answer: B [Carbon Dioxide]
Notes:
Sodium bicarbonate, commonly known as baking soda, is used in baking due to its ability to decompose above 70 degrees Celsius and release carbon dioxide. This chemical reaction is given by the equation 2 NaHCO3 – Na2CO3 + H2O + CO2. In baking, it reacts with other ingredients or decomposes at high temperatures to produce carbon dioxide, which causes the dough to rise, creating the fluffy texture in baked goods.
7. 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.
8. Which of the following is the softest metal?
[A] Cesium
[B] Lead
[C] Gold
[D] Silver
Show Answer
Correct Answer: A [ Cesium]
Notes:
Cesium is extremely reactive metal. It reacts with water even at −116 °C (−177 °F). It is the least electronegative element. Cesium is also the softest known metal. It is so soft that it can be cut with a butter knife.
9. Which of the following chemicals is also known as "butter of tin"?
[A] Stannic chloride
[B] Sodium perborate
[C] Potassium nitrate
[D] Magnesium hydroxide
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Correct Answer: A [ Stannic chloride]
Notes:
“Butter of Tin” is also known as tin tetrachloride pentahydrate. It is called “butter of tin” because of its physical appearance. Its chemical formula is SnCl4*5H2O or [SnCl4 (H2O)]*3H2O.
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.