Chemistry Objective (Multiple Choice) General Knowledge Questions & Answers for SSC-CGL, UPPSC, UPSC, NDA, CDS and UPSC Civil Services Prelims Examination.
11. What is the reason that despite being third most abundant element on the Earth’s surface and most abundant chemical substance in the universe, Hydrogen is not found as a gas in Earth’s atmosphere?
[A] It is very reactive and unstable gas
[B] It is so light that readily escapes earth’s gravity
[C] It is not found in free state in nature
[D] None of the above reasons
Show Answer
Correct Answer: B [ It is so light that readily escapes earth’s gravity]
Notes:
Under ordinary conditions on Earth, elemental hydrogen exists as the diatomic gas, H2. However, hydrogen gas is very rare in the Earth’s atmosphere (1 ppm by volume) because of its light weight, which enables it to escape from Earth’s gravity more easily than heavier gases. However, hydrogen is the third most abundant element on the Earth’s surface, mostly in the form of chemical compounds such as hydrocarbons and water. Hydrogen gas is produced by some bacteria and algae and is a natural component of flatus, as is methane, itself a hydrogen source of increasing importance.
12. Which of these is NOT a compound of carbon?
[A] Acetic acid
[B] Chloroform
[C] Caustic Soda
[D] Methane
Show Answer
Correct Answer: C [Caustic Soda]
Notes:
Caustic soda is a compound of sodium where as Acetic acid, Chloroform and Methane are the compounds of carbon.
13. Bell metal is an alloy of which of the following metals?
[A] Copper and Tin
[B] Copper and Mercury
[C] Copper and Lead
[D] Copper and Zinc
Show Answer
Correct Answer: A [Copper and Tin]
Notes:
Bell metal is a form of bronze with a higher tin content. It is an alloy of copper and tin (typically, 78% copper, 22% tin by mass). It is used for making bells and related instruments, such as cymbals.
14. Which of these methods is suitable to obtain the coloured component from black ink?
[A] Evaporation
[B] Sublimation
[C] Crystallisation
[D] All of the above
Show Answer
Correct Answer: A [Evaporation]
Notes:
The dye from water can be separated by the method of evaporation. Evaporation is used to separate the volatile component (solvent) from its non-volatile solute.
15. Which of the following is the correct order in terms of Iron content?
[A] Magnetite > Haematite >Siderite > Limonite
[B] Haematite> Magnetite >Siderite > Limonite
[C] Haematite > Magnetite > Limonite > Siderite
[D] Magnetite > Haematite > Limonite > Siderite
Show Answer
Correct Answer: D [Magnetite > Haematite > Limonite > Siderite]
Notes:
Magnetite > Haemetite > Limonite > Siderite . Magnetite has 72.4% iron content. Haematite has 70% iron content. Limonite has 55% iron content. Siderite has 48.2% iron content.
16. What do we call the ratio of number of fission produced by a given generation of neutrons to the number of fission of the preceding generation?
[A] Critical factor
[B] Energy factor
[C] Multiplication factor
[D] Moderation factor
Show Answer
Correct Answer: C [Multiplication factor]
Notes:
The multiplication factor is the ratio of number of fission produced by a given generation of neutrons to the number of fission of the preceding generation.
17. What do we call the reactions in which there is an exchange of ions between the reactants?
[A] Double Displacement reaction
[B] Decomposition reaction
[C] Displacement reaction
[D] Combination reaction
Show Answer
Correct Answer: A [Double Displacement reaction]
Notes:
The reactions in which there is an exchange of ions between the reactants are called double displacement reactions.
18. Which of the following is an organic compound?
[A] Carbon disulfide – CS2
[B] Carbon monoxide – CO
[C] Carbon tetrabromide – CBr4
[D] Carbon tetrachloride – CCl4
Show Answer
Correct Answer: D [Carbon tetrachloride – CCl4]
Notes:
Carbon tetrachloride – CCl4 is traditionally considered to be an organic compound despite not having H atoms.
19. Which of the following is produced when wood is burnt in a limited supply of oxygen?
[A] Charcoal
[B] Water gas
[C] Petroleum
[D] Paraffin
Show Answer
Correct Answer: A [Charcoal]
Notes:
When wood is burnt in a limited supply of oxygen, water and volatile materials present in it get removed and charcoal is left behind as the residue.
20. 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°.
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