General Science Chemistry MCQs
Chemistry Objective (Multiple Choice) General Knowledge Questions & Answers for SSC-CGL, UPPSC, UPSC, NDA, CDS and UPSC Civil Services Prelims Examination
61. Choose the correct statement about the compounds of carbon?
[A] Most carbon compounds are poor conductors of electricity
[B] Carbon forms covalent bonds
[C] Both a and b
[D] None
Show Answer
Correct Answer: C [Both a and b]
Notes:
Most carbon compounds are poor conductors of electricity. The forces of attraction between molecules of these compounds are not very strong. Carbon forms covalent bonds due to this sharing of four electrons of carbon with the electrons of other combining atoms.
62. What percentage of Human body is made up of carbon?
[A] 12
[B] 18.5
[C] 28.8
[D] 44.2
Show Answer
Correct Answer: B [18.5]
Notes:
Around 18.5% of Human body is made up of carbon. Carbon is the basic building block of most of the cells in the body. It helps with cellular respiration by which the human body releases energy stored in glucose.
63. Which of the following carbon compound is used as liquid rocket fuel?
[A] Carbon Tetrachloride
[B] Methane
[C] Propane
[D] All of Above
Show Answer
Correct Answer: B [Methane ]
Notes:
Methane is a saturated hydrocarbon. Its chemical formula is CH4. It is the main constituent of natural gas. Also, refined liquid methane is used as a rocket fuel. Use of Methane based rocket is currently in trend and SpaceX uses pure methane. Propane has inherent properties such as large mass and need of very low cooling point due to which it is not used as rocket fuel.
64. Which of the following is / are correct statements with respect to Graphite?
- It is the most stable phase of carbon at normal conditions
- It is made of made of sp3 hybridized carbon atoms
- It is good conductor of both heat and electricity
Select the correct option from the codes given below:
[A] Only 1 & 2
[B] Only 2 & 3
[C] Only 1 & 3
[D] 1, 2 & 3
Show Answer
Correct Answer: C [Only 1 & 3 ]
Notes:
Graphite is an allotrope of Carbon. It is a good conductor of electricity as well as heat. It is also most stable phase of carbon at normal conditions. It is made of made out of sp2 hybridized carbon atoms.
65. What is the general formula for alkyl groups?
[A] CnH2n+2
[B] CnH2n
[C] CnH2n-1
[D] CnH2n+1
Show Answer
Correct Answer: D [CnH2n+1]
Notes:
Alkyl groups are derived from alkanes by removal of one hydrogen atom. The general formula for alkyl groups is CnH2n+1.
66. Ethanoic acid is the main constituent of which of the following substances?
[A] Soap
[B] Vinegar
[C] Wine
[D] Curd
Show Answer
Correct Answer: B [Vinegar]
Notes:
Common name of Ethanoic acid is acetic acid and its main constituent of is a colourless liquid. 5-8% solution of acetic acid in water is called vinegar and is used widely as a preservative in pickles. The melting point of pure ethanoic acid is 290 K.
67. What is the common name of But-2-yne?
[A] Acetylene
[B] Methylacetylene
[C] Ethylacetylene
[D] Dimethylacetylene
Show Answer
Correct Answer: D [Dimethylacetylene]
Notes:
Dimethylacetylene is the common name of But-2-yne. Ethylacetylene is the common name of But-1-yne. Methylacetylene is the common name of Propyne. Acetylene is the common name of Ethyne.
68. Which gas is produced when Sodium ethanoate is heated with Soda lime?
[A] Methane
[B] Ethane
[C] Acetylene
[D] Ethene
Show Answer
Correct Answer: A [Methane]
Notes:
Sodium salts of carboxylic acids on heating with soda lime (mixture of sodium hydroxide and calcium oxide) give alkanes containing one carbon atom less than the carboxylic acid. This represents deCarboxylation.
69. Which of these alkanes has higher boiling point?
[A] Butane
[B] Methane
[C] Ethane
[D] Hexane
Show Answer
Correct Answer: D [Hexane]
Notes:
There is a steady increase in boiling point with the increase in molecular mass. This is due to the fact that the intermolecular van der Waals forces increase with increase of the molecular size or the surface area of the molecule.
70. What is the octane number of iso-octane?
Show Answer
Correct Answer: C [100]
Notes:
Octane number, also known as octane rating, are based on a scale on which iso-octane is 100, which means minimal knock, and heptane is 0. The higher the octane number, the more compression required for fuel ignition.
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