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 is not a correct statement about Bitumen?
[A] It’s a mixture of highly condensed polycyclic aromatic compounds
[B] Its is soluble in Carbon Disulphide
[C] SARA analysis is used to determine bitumen chemistry
[D] All of above are correct statements
Show Answer
Correct Answer: D [ All of above are correct statements ]
Notes:
Bitumen is a mixture of organic liquids that are highly viscous, black, sticky, soluble in carbon disulfide and composed of highly condensed polycyclic aromatic hydrocarbons.
2. Which element is responsible for the bright red color observed during the bursting of firecrackers?
[A] Strontium
[B] Sodium
[C] Sulfur
[D] Magnesium
Show Answer
Correct Answer: A [Strontium]
Notes:
The bright red color in fireworks is due to the presence of Strontium salts. The Strontium atom, upon yielding its energy in a quick burst upon heating, emits a brilliant red light. In fact, such properties of elements are used to identify them in a flame test, a classic method in chemistry labs across the globe.
3. What type of fiber is Rayon considered?
[A] A synthetic fiber
[B] A natural fiber
[C] A semi-synthetic fiber
[D] A synthetic detergent
Show Answer
Correct Answer: C [A semi-synthetic fiber]
Notes:
Rayon is considered a semi-synthetic fiber. It is made by regenerating natural materials into a usable form. Rayon fibers are derived from cellulose obtained from wood or related agricultural products. It was first commercially produced in 1905 by the Swiss firm J. R. Geigy, originally under the name “artificial silk”
4. Which among the following will undergo a chemical reaction depending on the pH of the solution?
[A] Calcium Oxide
[B] Zinc Oxide
[C] Ferric Oxide
[D] Ferrous Oxide
Show Answer
Correct Answer: B [Zinc Oxide]
Notes:
Zinc oxide (ZnO) can undergo a chemical reaction depending on the pH of the solution. In acidic conditions, it can react to form zinc ions (Zn²⁺), while in alkaline conditions, it can form zincates. This behavior is due to its amphoteric nature, which allows it to react with both acids and bases. In contrast, calcium oxide (CaO) is basic, ferric oxide (Fe₂O₃) is generally inert in neutral pH, and ferrous oxide (FeO) is less reactive in varying pH levels.
5. Which among the following gives hissing sound when dissolved into H2O?
[A] CaCO2
[B] Ca(OH)2
[C] CaO
[D] CaCl2
Show Answer
Correct Answer: C [CaO]
Notes:
The correct answer is CaO (calcium oxide), which is also known as quicklime. When CaO is dissolved in water, it reacts exothermically to form calcium hydroxide (Ca(OH)2), producing a hissing sound due to the rapid release of heat and steam. This reaction is a classic example of a vigorous exothermic reaction in chemistry. Calcium oxide is commonly used in construction and as a drying agent.
6. Which among the following can be used as a preservative in Tomato Juice?
[A] Sodium Chloride
[B] Sodium carbonate
[C] Sodium benzoate
[D] Sodium Lauril Sulphate
Show Answer
Correct Answer: C [Sodium benzoate]
Notes:
Sodium benzoate is commonly used as a preservative in food and beverages, including tomato juice. It inhibits the growth of mold, yeast, and some bacteria, extending shelf life. It is effective in acidic environments, such as those found in tomato products, where the pH is typically below 4.6. Sodium chloride (salt) can also act as a preservative but is primarily used for flavor. Sodium carbonate and sodium lauryl sulfate are not suitable preservatives for tomato juice.
7. Which among the following is Fool’s Gold?
[A] Copper Sulphate
[B] Iron Sulfide
[C] Brass
[D] Silver Bromide
Show Answer
Correct Answer: B [Iron Sulfide]
Notes:
The mineral pyrite or iron pyrite, also known as fool’s gold, is an iron sulfide with the chemical formula FeS2 (iron (II) disulfide). “Fool’s Gold” is technically known as pyrite or iron sulfide (FeS2) and is one of the most common sulfide minerals. Its nickname is “Fool’s Gold,” but it often contains a surprising amount of gold.
8. Which among the following compound is most commonly used in the Photochromic lenses?
[A] Potassium Dichromate
[B] Silver Chloride
[C] Potassium ferrate
[D] Ferric Chloride
Show Answer
Correct Answer: B [ Silver Chloride]
Notes:
Silver halides and most commonly silver Chloride is used in Photochromic lens. But for plastic photochromic lenses, some organic products such as oxazines and naphthopyrans are used.
9. How many electrons can the s-orbital accommodate?
[A] 1
[B] 2
[C] 8
[D] 16
Show Answer
Correct Answer: B [2]
Notes:
A the s-orbital can accommodate only two electrons, two groups (1 & 2) belong to the s-block of the Periodic Table.
10. Which of the following is not a mixture?
[A] Ocean water
[B] Table salt
[C] Air
[D] Soil
Show Answer
Correct Answer: B [Table salt]
Notes:
The composition of a mixture is variable whereas it is fixed for a compound. Table salt i.e. Sodium chloride is a compound and not a mixture.