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
71. When does a saturated hydrocarbon gives a sooty flame on burning?
[A] When the supply of oxygen is limited
[B] When the supply of oxygen is full
[C] A saturated hydrocarbon never gives a sooty flame on burning
[D] None of the above
Show Answer
Correct Answer: A [When the supply of oxygen is limited]
Notes:
Saturated hydrocarbons will generally give a clean flame while unsaturated carbon compounds will give a yellow flame with lots of black smoke. However, limiting the supply of air results in incomplete combustion of even saturated hydrocarbons giving a sooty flame.
72. Which of the following represents the mixture of carbon monoxide and nitrogen?
[A] Coal tar
[B] Producer gas
[C] Water gas
[D] All of the above
Show Answer
Correct Answer: B [Producer gas]
Notes:
Producer gas is a mixture of carbon monoxide and nitrogen. Producer gas is produced by passing air over red-hot coke. Coke is also used in the production of producer gas.
73. What is the H-C-H bond angle in a methane molecule?
[A] 120°
[B] 75°
[C] 109.5°
[D] 150°
Show Answer
Correct Answer: C [109.5°]
Notes:
According to VSEPR theory, methane has a tetrahedral structure which is multiplanar, in which carbon atom lies at the centre and the four hydrogen atoms lie at the four corners of a regular tetrahedron. All H-C-H bond angles are of 109.5°.
74. 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.
75. Which of the following polymer is obtained by the condensation reaction between ethylene glycol and terephthalic acid?
[A] Terelene
[B] PMMC
[C] PVC
[D] None of the above
Show Answer
Correct Answer: A [Terelene]
Notes:
Terelene is a polymer obtained by the condensation reaction between ethylene glycol and terephthalic acid. It is widely used in making wash and wear fabrics as it has low absorbing power.
76. Which of these is a biodegradable polymer?
[A] PLA
[B] PCL
[C] PGA
[D] All of the above
Show Answer
Correct Answer: D [All of the above]
Notes:
A large number of bio degradable polymers are now available will replace non-bio-degradable polymers as their cost reduces. Some of the important biodegradable polymers are PHBV, PGA, PLA and PCL.
77. Which of the following metal is the key component of Vitamin B12?
[A] Iron
[B] Zinc
[C] Copper
[D] Cobalt
Show Answer
Correct Answer: D [Cobalt]
Notes:
Cobalt is the key component of Vitamin B12. Cobalt is a metal with atomic number 27. The cobalt metal produced by reductive smelting is hard, lustrous and silver-gray in colour.
78. Which of the following metals can easily be cut with a knife?
[A] Sodium
[B] Manganese
[C] Zinc
[D] Tin
Show Answer
Correct Answer: A [Sodium]
Notes:
Out of all the given options, Sodium is a softer metal and can be easily cut with a knife. It is a highly reactive metal which is silvery white in colour.
79. Which of these metals is commonly used in tanning of leather?
[A] Phosphorous
[B] Indium
[C] Manganese
[D] Chromium
Show Answer
Correct Answer: D [Chromium]
Notes:
Chromium(III) salts are used in the tanning of leather. Chromium is a steely-grey, lustrous, hard and brittle transition metal which is also used as an additive in stainless steel.
80. What are the structures formed by the soap molecules, during cleansing, known as?
[A] Stereates
[B] Esters
[C] Micelles
[D] Tubes
Show Answer
Correct Answer: C [Micelles]
Notes:
The ionic-end of soap dissolves in water while the carbon chain dissolves in oil. The soap molecules form structures called micelles where one end of the molecules is towards the oil droplet while the ionic-end faces outside.
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