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 a thermosetting plastic?
[A] Polythene
[B] Bakelite
[C] Polyvinyl chloride
[D] Casseine
Show Answer
Correct Answer: B [Bakelite]
Notes:
Bakelite is a thermosetting plastic formed from phenol and formaldehyde, used in electrical insulators and cookware handles. Unlike thermoplastics, it hardens irreversibly when heated and cannot be remolded. It was the first synthetic plastic, invented by Leo Baekeland in 1907.
2. What happens to ozone’s volume when it is heated?
[A] Increases
[B] Decreases
[C] Remains unchanged
[D] First increases, then decreases
Show Answer
Correct Answer: A [Increases]
Notes:
According to Charles’s Law, for gases at constant pressure, volume increases with temperature. Heating ozone increases the kinetic energy of molecules, expanding its volume if pressure is constant. Ozone (O₃) behaves like other gases, expanding when heated. This law applies to all ideal gases and ozone approximates ideal behavior under moderate conditions.
3. 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.
4. The largest component of Coal gas is__?
[A] Methane
[B] Hydrogen
[C] Carbon Dioxide
[D] Carbon Monoxide
Show Answer
Correct Answer: B [ Hydrogen]
Notes:
Typical composition of the Coal gas is as follows: •Hydrogen 50% •Methane 35% •Carbon monoxide 10% •Ethylene 5%
5. Which of the following is correct about the first ionization enthalpy of alkaline earth metals?
[A] It is higher than corresponding Group 1 metals
[B] It is lower than corresponding Group 1 metals
[C] No fix pattern exist
[D] None of the above
Show Answer
Correct Answer: A [It is higher than corresponding Group 1 metals]
Notes:
The first ionization enthalpy of these metals is higher than corresponding Group 1 metals due to the small size of these elements compared to the corresponding alkali metals. The second ionization enthalpy of these metals is lower than corresponding alkali metals.
6. Which of the following is correct about Potassium carbonate?
[A] Its chemical formula is K CO3
[B] It is a salt which is white in colour
[C] It is used in the production of soap
[D] All of the above
Show Answer
Correct Answer: D [All of the above]
Notes:
Potassium carbonate is a salt which is white in colour. It is used in the production of soap. Its chemical formula is K2 CO3.
7. 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.
8. Which of the following Metal-Ore pairs is not correct?
[A] Iron – Magnetite
[B] Aluminium – Bauxite
[C] Gold – Calaverite
[D] Calcium – Carnalite
Show Answer
Correct Answer: D [Calcium – Carnalite]
Notes:
Carnalite is an ore of Potassium. It’s a hydrated potassium magnesium chloride. The chemical formula of Carnalite is KCl. MgCl2 . 6H2O.
9. What is the general trend for electronegativity in a group of the periodic table as we move from top to bottom?
[A] It increases
[B] It decreases
[C] It remains constant
[D] None
Show Answer
Correct Answer: B [It decreases]
Notes:
Electronegativity generally increases across a period from left to right (say from lithium to fluorine) and decrease down a group (say from fluorine to astatine) in the periodic table.
10. Which of these is a Thermoplastic polymer?
[A] Terylene
[B] Polythene
[C] PVC
[D] All of the above
Show Answer
Correct Answer: D [All of the above]
Notes:
Thermoplastic polymers are linear polymers with very few cross linkages or no cross linkages at all. Polythene, PVC, polystyrene are addition type thermoplastics and Terylene, nylon are condensation type thermoplastics.
