Chemistry MCQs
Chemistry Objective (Multiple Choice) General Knowledge Questions & Answers for SSC-CGL, UPPSC, UPSC, NDA, CDS and UPSC Civil Services Prelims Examination.
1. Dalton’s name is associated with which of the following terms?
[A] Electron
[B] Proton
[C] Atom
[D] Neutron
Show Answer
Correct Answer: C [Atom]
Notes:
John Dalton introduced the atomic theory into chemistry. The main points of Dalton’s atomic theory are (1) Elements are made of extremely small particles called atoms. (2) Atoms of a given element are identical in size, mass and other properties; atoms of different elements differ in size, mass and other properties.(3) Atoms cannot be subdivided, created or destroyed. (4) Atoms of different elements combine in simple whole-number ratios to form chemical compounds. (5) In chemical reactions, atoms are combined, separated or rearranged.
2. Which among the following is a Noble Gas?
[A] Nitrogen
[B] Hydrogen
[C] Oxygen
[D] Helium
Show Answer
Correct Answer: D [Helium]
Notes:
The noble gases are the chemical elements in group 18 of the periodic table. They are the most stable due to having the maximum number of valence electrons their outer shell can hold. This chemical series contains helium, neon, argon, krypton, xenon, and radon.
3. Which among the following is major component of Gobar Gas?
[A] Butane
[B] Ethane
[C] Propane
[D] Metahne
Show Answer
Correct Answer: D [Metahne]
Notes:
Gobar Gas or Biogas is mostly methane (CH4) and carbon dioxide (CO2) and may have small amounts of hydrogen sulfide (H2S), moisture and siloxanes.
4. Out of the following options, which group of elements is typically found in a free state?
[A] Group 11 elements
[B] Group 12 elements
[C] Group 13 elements
[D] Group 14 elements
Show Answer
Correct Answer: A [Group 11 elements]
Notes:
Group 11 elements, which include copper, silver, and gold, have been known since ancient times. These elements are found in the Earth’s crust in a free or native state, due to their low reactivity compared to other elements. This is why these elements were used by ancient civilizations for crafting tools, jewelry, and early forms of money.
5. Water at 4 degree centigrade has____?
[A] minimum density
[B] maximum density
[C] No density
[D] None of the above
Show Answer
Correct Answer: B [maximum density]
Notes:
Water at 4 degrees Celsius has maximum density. This is due to the unique molecular structure of water, which allows it to reach its highest density at this temperature. As water cools from higher temperatures, it becomes denser until it reaches 4 degrees. below this temperature, it begins to expand, making ice less dense than liquid water. This phenomenon is crucial for aquatic life, as it allows ice to float, insulating the water below.
6. The chemical oxygen demand COD test is commonly used to measure which of the following?
[A] amount of organic compounds in water
[B] amount of oxygen in water
[C] amount of oxygen in a chemical
[D] amount of oxygen used in a oxygenation process
Show Answer
Correct Answer: A [amount of organic compounds in water]
Notes:
chemical oxygen demand is a measure of water quality and is amount of organic pollutants found in surface water. Potassium permanganate has been used for many years to measure COD
7. Sodium bicarbonate decomposes above 70 °C, making it usable in bakery products. What end product of this thermal decomposition process contributes to its use in baking?
[A] Hydrogen
[B] Carbon Dioxide
[C] Water Vapor
[D] Sodium Carbonate
Show Answer
Correct Answer: B [Carbon Dioxide]
Notes:
Sodium bicarbonate, commonly known as baking soda, is used in baking due to its ability to decompose above 70 degrees Celsius and release carbon dioxide. This chemical reaction is given by the equation 2 NaHCO3 – Na2CO3 + H2O + CO2. In baking, it reacts with other ingredients or decomposes at high temperatures to produce carbon dioxide, which causes the dough to rise, creating the fluffy texture in baked goods.
8. The colors in the fine cut diamond are because of which among the following?
[A] Variance in transparency of diamond
[B] Variance in index of refraction
[C] Presence of Impurities
[D] Existence of definite planer layers
Show Answer
Correct Answer: C [Presence of Impurities]
Notes:
Pure diamond should transmit visible light and appear as a clear colorless crystal. Colors in diamond originate from lattice defects and impurities. The diamond crystal lattice is exceptionally strong and only atoms of nitrogen, boron and hydrogen can be introduced into diamond during the growth at significant concentrations (up to atomic percents). Nitrogen gives yellowish color while the Boron gives bluish color.
9. 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.
10. Which of the following laws is used as a rule to predict the solubility of gases in metals?
[A] Dalton’s Law
[B] Sievert’s law
[C] Graham’s law
[D] Henry’s law
Show Answer
Correct Answer: B [ Sievert’s law]
Notes:
Sievert’s law is used as a rule in physical metallurgy to predict the solubility of gases in metals.
