Chemistry MCQs
Chemistry Objective (Multiple Choice) General Knowledge Questions & Answers for SSC-CGL, UPPSC, UPSC, NDA, CDS and UPSC Civil Services Prelims Examination.
1. Which of the following is the most active chemically?
[A] Chlorine
[B] Flourine
[C] Lithium
[D] Iodine
Show Answer
Correct Answer: B [Flourine]
Notes:
Fluorine is most active because it has the highest electronegativity.
2. Which among the following kinds of glass is used generally in making of the Bullet proof screens?
[A] Pyrex glass
[B] Jena glass
[C] Reinforced Glass
[D] Flint Glass
Show Answer
Correct Answer: C [Reinforced Glass]
Notes:
Reinforced Glass or Toughened glass or tempered glass is a kind of safety glass is used as s a component of bulletproof glass, for diving masks, and various types of plates and cookware.
3. When a piece of quicklime is dipped in water, it gives bubbles. This bubbling is due to which of the following ?
[A] Oxygen
[B] Carbon Dioxide
[C] Water Vapour
[D] Hydrogen
Show Answer
Correct Answer: C [Water Vapour]
Notes:
When quicklime (calcium oxide) is added to water, it reacts exothermically to form calcium hydroxide (slaked lime). This reaction produces heat and releases water vapor, which causes bubbling. The reaction can be represented as: [ ext{CaO} + ext{H}_2 ext{O}
ightarrow ext{Ca(OH)}_2 + ext{heat} ] Trivia: Quicklime is used in various applications, including steelmaking and water treatment, and was historically used in ancient construction.
4. Which among the following impurity in drinking water causes the “Bamboo Spine” disorder?
[A] Nitrate
[B] Fluorides
[C] Arsenic
[D] Sulphides
Show Answer
Correct Answer: B [ Fluorides]
Notes:
Ankylosing Spondylitis is a chronic, inflammatory arthritis and autoimmune disease that mainly affects joints in the spine and the sacroiliac joints in the pelvis. It tends to affect the spine and in late stages, the spine will fuse and this has given rise to the term “bamboo spine”. It is mainly caused due to impurities in drinking water associated with fluorides.
5. Which of the following is not an isotope of Hydrogen?
[A] Protium
[B] Para hydrogen
[C] Deuterium
[D] Tritium
Show Answer
Correct Answer: B [ Para hydrogen]
Notes:
The three most stable isotopes of hydrogen: Protium, Deuterium and Tritium. Para hydrogen is not an isotope of hydrogen. Molecules of hydrogen in which the spins of both the nuclei are in the opposite direction are called Para hydrogen.
6. 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.
7. Which of the following is the composition of vinegar?
[A] 65-75% solution of acetic acid in water
[B] 45-60% solution of acetic acid in water
[C] 28-35% solution of acetic acid in water
[D] 5-8% solution of acetic acid in water
Show Answer
Correct Answer: D [5-8% solution of acetic acid in water]
Notes:
5-8% solution of acetic acid in water is called vinegar and is used widely as a preservative in pickles
8. Which of the following is NOT correct about Ethanol?
[A] It is a good solvent
[B] It gives out hydrogen when reacted with Sodium
[C] It is an odorless liquid
[D] All are correct
Show Answer
Correct Answer: C [It is an odorless liquid]
Notes:
Ethanol is a good solvent and reacts with sodium leading to the evolution of hydrogen. It is a colorless liquid with a slight characteristic odor.
9. Which of the following mixture can be separated by Fractional distillation method?
[A] Air
[B] Crude oil
[C] Chlorosilanes
[D] All of the above
Show Answer
Correct Answer: D [All of the above]
Notes:
Fractional distillation method is used to separate a mixture of two or more miscible liquids for which the difference in boiling points is less than 25 K. example: Air, crude oil, chlorosilanes etc.
10. What will be the number of neutrons in an atom having atomic number 35 and mass number 80?
[A] 35
[B] 45
[C] 55
[D] 80
Show Answer
Correct Answer: B [45]
Notes:
The total number of nucleons is termed as mass number (A) of the atom. In this case, mass number is 80. Therefore, sum of the number of neutrons and protons is 80. As atomic number is 35, we know that number of protons is 35. Hence, number of neutrons = 80-35 = 45.
