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 among the following is an example of a Chemical Change?
[A] Rusting of iron
[B] Magnetisation of iron
[C] Melting of iron
[D] Heating of iron
Show Answer
Correct Answer: A [Rusting of iron ]
Notes:
Rust is an iron oxide, a usually red oxide formed by the redox reaction of iron and oxygen in the presence of water or air moisture. Rusting of Iron is a chemical change.
2. Which among the following is known as White Vitriol?
[A] Zinc Sulphate
[B] Zinc Chloride
[C] Zinc Phosphate
[D] Zinc oxide
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Correct Answer: A [Zinc Sulphate]
Notes:
Zinc sulfate is the inorganic compound with the formula ZnSO4 and historically known as “white vitriol” Zinc sulfate is an inorganic compound and dietary supplement.
3. According to Avogadro’s hypothesis, equal volumes of gases contain equal number of?
[A] Atoms
[B] Molecules
[C] Particles
[D] Electrons
Show Answer
Correct Answer: B [Molecules]
Notes:
Avogadro’s hypothesis was proposed by Amedeo Avogadro in 1811. It states that equal volumes of all gases, at the same temperature and pressure, contain equal numbers of molecules. Avogadro’s number is defined as 6.022×10^23 molecules per mole. This hypothesis was crucial for determining molecular weights and led to the development of the ideal gas law.
4. Which of these is not considered an ore?
[A] Chalcopyrite
[B] Sphalerite
[C] Cinnabar
[D] Andesite
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Correct Answer: D [Andesite]
Notes:
Andesite is an igneous volcanic rock with intermediate composition and is not used as an ore. Chalcopyrite is a major copper ore, sphalerite is the primary ore of zinc, and cinnabar is the main ore of mercury. Andesite mainly consists of plagioclase, pyroxene, and amphibole minerals and forms in volcanic arcs associated with subduction zones.
5. How many parts are of other metals in a 17 carat Gold?
[A] 3
[B] 5
[C] 7
[D] 9
Show Answer
Correct Answer: C [7]
Notes:
In 17 carat gold, the composition is 17 parts gold and 7 parts other metals, making it 70.6% gold. The term “carat” refers to the purity of gold, with 24 carats being pure gold. Thus, 17 carat gold contains 7 parts of other metals, which can include copper, silver, or palladium, used to enhance durability and alter color.
6. Acid rain is capable of damaging the buildings and historic monuments which are made up of rocks such as limestone and marble. Which among the following is the end product of such reaction?
[A] Quick Lime
[B] Calcium Carbonate
[C] Calcium Hydroxide
[D] Gypsum
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Correct Answer: D [Gypsum]
Notes:
When sulfuric, and nitric acids, present in the acid rain reacts with the calcite in marble and limestone, it get dissolve and formed gypsum and washed off by the water. The rain can dissolve limestone and marble through direct contact.
7. Which of the following is correct about Ammonia?
[A] The ammonia molecule is trigonal pyramidal in shape
[B] Ammonia gas is light blue in colour
[C] its aqueous solution is highly basic
[D] Ammonia gas is odorless
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Correct Answer: A [The ammonia molecule is trigonal pyramidal in shape]
Notes:
Ammonia is a colourless gas with a pungent odour. Its aqueous solution is weakly basic due to the formation of OH– ions. The ammonia molecule is trigonal pyramidal in shape.
8. Which of the following is NOT correct about Phosphine?
[A] The chemical formula is PH3
[B] The electronic structure is like Ammonia
[C] It is odorless
[D] it is used as a dopant in semiconductor industries
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Correct Answer: C [It is odorless]
Notes:
Phosphine is PH3. The electronic structure of Phosphine (pyramidal structure) is like Ammonia. It is a colourless gas and has a spoiled fish smell. It is used as a dopant in semiconductor industries.
9. Which of the following is the composition of vinegar?
[A] 65-75% solution of acetic acid in water
[B] 45-60% solution of acetic acid in water
[C] 28-35% solution of acetic acid in water
[D] 5-8% solution of acetic acid in water
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Correct Answer: D [5-8% solution of acetic acid in water]
Notes:
5-8% solution of acetic acid in water is called vinegar and is used widely as a preservative in pickles
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.
