Chemistry MCQs
Chemistry Objective (Multiple Choice) General Knowledge Questions & Answers for SSC-CGL, UPPSC, UPSC, NDA, CDS and UPSC Civil Services Prelims Examination.
1. The term “white coal” sometimes referred to which of the following?
[A] Geothermal Electricity
[B] Wind Energy
[C] Hydroelectricity
[D] Biomass Energy
Show Answer
Correct Answer: C [Hydroelectricity]
Notes:
The term white coal was used for Hydroelectricity, particularly in Europe, because of its capability to produce more energy than any other source except coal. The term was coined by a French Engineer Aristide Bèrges.
2. Which among the following is a Noble Gas?
[A] Nitrogen
[B] Hydrogen
[C] Oxygen
[D] Helium
Show Answer
Correct Answer: D [Helium]
Notes:
The noble gases are the chemical elements in group 18 of the periodic table. They are the most stable due to having the maximum number of valence electrons their outer shell can hold. This chemical series contains helium, neon, argon, krypton, xenon, and radon.
3. Which among the following gas has lowest auto-ignition temperature?
[A] Methane
[B] Hydrogen
[C] Ethylene
[D] Carbon Di Sulphide
Show Answer
Correct Answer: D [Carbon Di Sulphide]
Notes:
The auto-ignition temperature of a liquid, gas or vapor is the temperature at which the substance will ignite without any external heat source. Here is the temperature of some gases:
Methane -580 °C
Hydrogen -560 °C
Propane -493 °C
Ethylene -425 °C
Acetylene -305 °C
Naphtha -290 °C
Carbon disulfide -102 °C
4. 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.
5. Normal” rainfall is slightly acidic (and a pH of 5.6 has been assigned which might be somewhere near 5 ) because of the presence of _______?
[A] Nitric Oxide
[B] Sulphuric Acid
[C] Nitric Acid
[D] Carbonic Acid
Show Answer
Correct Answer: D [Carbonic Acid]
Notes:
Normal rainfall is slightly acidic due to the presence of carbonic acid, which forms when carbon dioxide (CO2) dissolves in water. The pH of normal rainwater is typically around 5.6, making it mildly acidic. This natural acidity is a result of the CO2 in the atmosphere, which is produced by respiration, combustion, and other natural processes.
6. Which among the following is produced when we pass chlorine into slaked lime?
[A] DDT
[B] Baking Powder
[C] Bleaching Powder
[D] Gypsum
Show Answer
Correct Answer: C [ Bleaching Powder]
Notes:
Bleaching powder is made by passing Cl2 into slaked lime. Though bleaching powder is often written as Ca(OCl)2 , it is really a mixture and not a compound.
7. Which of the following is NOT correct about Alkynes?
[A] They contain at least two triple bond between two carbon atoms
[B] The number of hydrogen atoms is less in alkynes as compared to alkenes
[C] The general formula of Alkynes is CnH2n–2
[D] All are correct
Show Answer
Correct Answer: A [They contain at least two triple bond between two carbon atoms]
Notes:
Alkynes contain at least one triple bond between two carbon atoms. The number of hydrogen atoms is less in alkynes as compared to alkenes or alkanes. Their general formula is CnH2n–2.
8. What is dry ice?
[A] solidified form of Carbon dioxide
[B] frozen heavy water
[C] isotope of Hydrogen
[D] popular name of Benzene
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Correct Answer: A [solidified form of Carbon dioxide]
Notes:
Carbon dioxide can be obtained as a solid in the form of dry ice by allowing the liquified CO2 to expand rapidly.
9. Which of the following is not a mixture?
[A] Ocean water
[B] Table salt
[C] Air
[D] Soil
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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.
10. What is Tyndall effect?
[A] scattering of a beam of light by the particles of a suspension
[B] refraction of a beam of light by the particles of a solution
[C] scattering of a beam of light by the particles of a colloid
[D] reflection of a beam of light by the particles of a suspension
Show Answer
Correct Answer: C [scattering of a beam of light by the particles of a colloid]
Notes:
The scattering of a beam of light by the particles of a colloid is called the Tyndall effect.
