Chemistry MCQs
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 among the following compound is most commonly used in the Photochromic lenses?
[A] Potassium Dichromate
[B] Silver Chloride
[C] Potassium ferrate
[D] Ferric Chloride
Show Answer
Correct Answer: B [ Silver Chloride]
Notes:
Silver halides and most commonly silver Chloride is used in Photochromic lens. But for plastic photochromic lenses, some organic products such as oxazines and naphthopyrans are used.
13. Which of the following is correct about the atomic and ionic radii of the alkaline earth metals?
[A] it is smaller than corresponding alkali metals in the same periods
[B] it is larger than corresponding alkali metals in the same periods
[C] It is same as the corresponding alkali metals in the same periods
[D] None of the above
Show Answer
Correct Answer: A [it is smaller than corresponding alkali metals in the same periods]
Notes:
The atomic and ionic radii of the alkaline earth metals are smaller than corresponding alkali metals in the same periods due to the increased nuclear charge in these elements.
14. Galena is an ore of which of the following metals?
[A] Tin
[B] Copper
[C] Lead
[D] Gold
Show Answer
Correct Answer: C [Lead]
Notes:
Galena is an ore of Lead. It is also known as lead glance. It is the natural mineral form of lead sulfide (PbS).
15. Which of the following is emitted in Beta-decay process?
[A] Electron
[B] Positron
[C] Both a and b
[D] None
Show Answer
Correct Answer: C [Both a and b]
Notes:
In beta decay, a nucleus spontaneously emits an electron (βdecay) or a positron (β+decay). One can never predict which nucleus will undergo decay.
16. Which of the following elements is identified by the 7th group and 4th period of the modern periodic table?
[A] Copper
[B] Iron
[C] Manganese
[D] Chromium
Show Answer
Correct Answer: C [Manganese]
Notes:
Manganese is placed in the 7th group and 4th period of the modern periodic table. Its Atomic number is 25 and is placed group VII A.
17. What is the process known as where acids produce ions when dissolved in water?
[A] Vulcanisation
[B] Dissociation
[C] Scattering
[D] None of the above
Show Answer
Correct Answer: B [Dissociation]
Notes:
When an acid dissolves in water, a covalent bond between an electronegative atom and a hydrogen atom is broken by heterolytic fission. It gives out a proton (H+) and a negative ion. This process is called as Disassociation.
18. What do we call the molar conductivity when the concentration approaches zero?
[A] Reacting molar conductivity
[B] Zero level molar conductivity
[C] Limiting molar conductivity
[D] Ideal molar conductivity
Show Answer
Correct Answer: C [Limiting molar conductivity]
Notes:
When concentration approaches zero, the molar conductivity is known as limiting molar conductivity.
19. Which of the following is the product of the reaction between Ethanoic acid and Sodium hydrogen carbonate?
[A] Ethyne
[B] Sodium acetate
[C] Ethanol
[D] Sodium hydroxide
Show Answer
Correct Answer: B [Sodium acetate]
Notes:
Sodium acetate is produced when Ethanoic acid and Sodium hydrogen carbonate reacts with each other. Ethanoic acid reacts with carbonates and hydrogen carbonates to give rise to a salt, carbon dioxide and water.
20. Which of these non-metals is mainly used as an inert shielding gas?
[A] Xenon
[B] Hydrogen
[C] Argon
[D] Krypton
Show Answer
Correct Answer: C [ Argon ]
Notes:
Argon is used mainly to provide an inert atmosphere in high temperature metallurgical processes (arc welding of metals or alloys). It is also used for filling electric bulbs.
