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 of the following best describes the nature of Froth and Foam?
[A] Solid suspended in gas
[B] Liquid suspended in gas
[C] Gas suspended in liquid
[D] Gas suspended in solid
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Correct Answer: C [Gas suspended in liquid]
Notes:
Froth and foams are examples of “gas suspended in liquid”. They are typically created when gas bubbles are dispersed in a liquid. This physical phenomenon is commonly observed in many daily life scenarios such as soap lather and carbonated drinks. Technically, they are a special case of colloid where little blobs of one liquid are dispersed in another and show the property of surface tension.
2. How many noble gases occur naturally?
[A] Three
[B] Four
[C] Five
[D] Six
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Correct Answer: D [Six]
Notes:
Noble gases are characterized by their low reactivity. The reason for this is their full electron shell, which makes them very stable and unlikely to engage in chemical reactions. The six noble gases that occur naturally are helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and the radioactive radon (Rn). Despite the inertness of noble gases, some of them like Xenon are known to form compounds.
3. Which among the following is the main constituent of malleable metal alloy Pewter ?
[A] Copper
[B] Zinc
[C] Tin
[D] Bismuth
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Correct Answer: C [Tin]
Notes:
Pewter is primarily composed of tin, typically around 85-95%, with the remainder often consisting of copper, antimony, or bismuth. Historically, pewter was used for making utensils and decorative items due to its malleability and low melting point. The use of tin in pewter dates back to ancient civilizations, including the Romans and Egyptians, who valued it for its corrosion resistance and ease of casting.
4. What is Carbamide?
[A] A Pesticide
[B] A Fertilizer
[C] A Textile Dye
[D] An Explosive
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Correct Answer: B [A Fertilizer]
Notes:
Carbamide is another name of Urea, an organic compound with chemical formula CO(NH2)2. This name indicates that Urea is an amide in which two –NH2 groups are joined by a carbonyl (C=O) functional group.
5. How does vulcanization make natural rubber more durable?
[A] The long polymer chains are shortened
[B] The rubber loses water and sticky substances
[C] The short polymer chains are lengthened
[D] Cross links form between the polymer chains
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Correct Answer: D [Cross links form between the polymer chains]
Notes:
Vulcanization introduces sulfur cross-links between poly-isoprene chains in natural rubber, restricting movement, which increases stiffness, elasticity, and durability. This chemical modification prevents rubber from becoming sticky or brittle, significantly improving its mechanical properties for industrial and commercial use.
6. Which of the following statements is incorrect about Stainless Steel?
[A] it is also known as inox steel
[B] It is an alloy of Iron, cobalt and nickel
[C] It is corrosion resistant
[D] molybdenum is added to increase corrosion resistance in reducing acids
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Correct Answer: B [It is an alloy of Iron, cobalt and nickel]
Notes:
Stainless steel is also known as inox steel. It is an alloy of Iron, chromium and nickel. It is corrosion resistant and molybdenum is added to increase corrosion resistance in reducing acids.
7. What do we call the device which uses electrical energy to carry non-spontaneous chemical reactions?
[A] Voltaic cell
[B] Galvanic cell
[C] Daniel cell
[D] Electrolytic cell
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Correct Answer: D [Electrolytic cell]
Notes:
An electrolytic cell is an electrochemical cell which uses electrical energy to drive a non-spontaneous redox reaction.
8. What percent of Carbon is present in the earth’s crust?
[A] 10%
[B] 76%
[C] 0.18%
[D] 38.2%
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Correct Answer: C [0.18%]
Notes:
Carbon is the 15th most abundant element in the earth’s crust with a percentage of 0.18%. Oxygen is the most abundant element at 46%, followed by silicon at 27% and aluminum at 8.1.
9. What is the reason for the presence of the vast number of organic compounds in nature?
[A] Carbon exists in free state
[B] Catenation property of carbon
[C] Low atomic mass of carbon
[D] None of the above
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Correct Answer: B [Catenation property of carbon]
Notes:
Because of the catenation property of carbon, vast number of organic compounds are present in nature. Catenation refers to the linkage of atoms of the same element into longer chains.
10. What do we call the compounds formed by the linking of carbon by single bonds in between them?
[A] Saturated compounds
[B] Unsaturated compounds
[C] Monovalent compounds
[D] Ionic compounds
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Correct Answer: A [Saturated compounds]
Notes:
The compounds formed by the linking of carbon by single bonds in between them are known as Saturated compounds. Alkanes are saturated compounds with Methane (CH4) being one of the simplest saturated compounds.