Chemistry MCQs
Chemistry Objective (Multiple Choice) General Knowledge Questions & Answers for SSC-CGL, UPPSC, UPSC, NDA, CDS and UPSC Civil Services Prelims Examination.
1. What are the main constituents of LPG?
[A] Methane, Hexane, Ethane
[B] Methane, Butane, Propane
[C] Ethane, Pentane, Hexane
[D] Ethane, Methane, Pentane
Show Answer
Correct Answer: B [Methane, Butane, Propane]
Notes:
LPG is composed hydrocarbons containing three or four carbon atoms. The normal components of LPG thus, are propane (C3H8), butane (C4H10) and Methane (CH4). Small concentrations of other hydrocarbons may also be present.
2. Which among following is also known as white gold?
[A] Nickel
[B] Rhodium
[C] Platinum
[D] Palladium
Show Answer
Correct Answer: C [Platinum]
Notes:
Platinum is a naturally white metal. It doses not need to be alloyed for color. Due to its appearance as white, it is commonly known as White Gold.
3. Which of the following statements about the chemical nature of Diamond and Graphite is incorrect?
[A] The density of Diamond is greater than that of Graphite
[B] Diamond is chemically unreactive whereas Graphite mildly reacts with certain elements
[C] Both Diamond and Graphite are excellent conductors of electricity
[D] None of the above statements is incorrect
Show Answer
Correct Answer: C [Both Diamond and Graphite are excellent conductors of electricity]
Notes:
Diamond and graphite are both forms of carbon but they exhibit different properties due to variations in their bonding arrangements. Diamond does not conduct electricity as each carbon atom in diamond is covalently bonded to four other carbon atoms, leaving no free electrons to conduct electricity. On the other hand, graphite is a good conductor of electricity due to its layered structure which leaves free electrons between the layers.
4. How many parts are of other metals in a 17 carat Gold?
[A] 3
[B] 5
[C] 7
[D] 9
Show Answer
Correct Answer: C [7]
Notes:
In 17 carat gold, the composition is 17 parts gold and 7 parts other metals, making it 70.6% gold. The term “carat” refers to the purity of gold, with 24 carats being pure gold. Thus, 17 carat gold contains 7 parts of other metals, which can include copper, silver, or palladium, used to enhance durability and alter color.
5. Which among the following kinds of Chemical reactions cause the rocks turn red or yellowish?
[A] Hydration
[B] Oxidation
[C] Carbonation
[D] Exfoliation
Show Answer
Correct Answer: B [Oxidation]
Notes:
The correct answer is Oxidation. This reaction occurs when minerals in rocks, particularly iron-bearing minerals, react with oxygen. This process can lead to the formation of iron oxides, which give rocks a reddish or yellowish hue. For example, rusting of iron in rocks is a common oxidation reaction. Oxidation is a important weathering process, contributing to soil formation and landscape changes.
6. Which among the following will emit maximum mass of carbon dioxide , when the same quantity is burnt of all of them?
[A] Kerosene
[B] Natural Gas
[C] Gasoline
[D] Propane
Show Answer
Correct Answer: A [Kerosene]
Notes:
The carbon content of Kerosene is higher than the other fuels mentioned in the option, that is why it will emit maximum mass of carbon dioxide, when the same quantity is burnt.
7. Which of the following is correct about Ammonia?
[A] The ammonia molecule is trigonal pyramidal in shape
[B] Ammonia gas is light blue in colour
[C] its aqueous solution is highly basic
[D] Ammonia gas is odorless
Show Answer
Correct Answer: A [The ammonia molecule is trigonal pyramidal in shape]
Notes:
Ammonia is a colourless gas with a pungent odour. Its aqueous solution is weakly basic due to the formation of OH– ions. The ammonia molecule is trigonal pyramidal in shape.
8. Which of the following decays represents the decay of Uranium-238 to thorium-234?
[A] Alpha decay
[B] Beta decay
[C] Gamma decay
[D] None of the above
Show Answer
Correct Answer: A [Alpha decay]
Notes:
The radioactive decay of uranium-238 to thorium-234, with the emission of a helium nucleus, is a well-known example of alpha decay.
9. Who gave the law of octaves for arrangement of elements?
[A] Lothar Meyer
[B] Dmitri Mendeleev
[C] John Alexander Newlands
[D] Johann Dobereiner
Show Answer
Correct Answer: C [John Alexander Newlands]
Notes:
Newland law of octaves states that If the elements are arranged in order of their increasing atomic weights, every 8th element had similar properties to the first one. It was similar as the first and eighth note in music.
10. 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.
