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 iron ore contains the highest percentage of iron content?
[A] Hematite
[B] Siderite
[C] Magnetite
[D] Limonite
Show Answer
Correct Answer: C [Magnetite]
Notes:
Magnetite (Fe3O4) typically contains about 70% iron by weight. It is black in color and strongly magnetic. Hematite (Fe2O3) contains about 60–70% iron. Limonite contains 35–50% iron. Siderite (FeCO3) contains about 48% iron. Magnetite is widely mined due to its high iron concentration compared to other ores.
2. 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.
3. Cassiterite is most important source of which of these metals?
[A] Nickel
[B] Tin
[C] Tungsten
[D] Silver
Show Answer
Correct Answer: B [Tin ]
Notes:
Cassiterite is a mineral that is primarily composed of tin dioxide (SnO2). It is the most important source of tin, and is also used as a semi-precious gemstone. Cassiterite is typically found in igneous and metamorphic rocks, and is often associated with other minerals such as quartz, feldspar, and mica. It has a high melting point and is resistant to weathering, making it a useful material for many industrial applications. The name “cassiterite” comes from the Greek word “kassiteros,” which means “tin.”
4. 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.
5. Which of the following represents the general formula for alkanes?
[A] CnH2n
[B] CnH2n-2
[C] CnH2n+2
[D] CnHn
Show Answer
Correct Answer: C [CnH2n+2]
Notes:
Alkanes are saturated open chain hydrocarbons containing carbon – carbon single bonds.
6. 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.
7. Which of the following methods is used to purify Titanium metal?
[A] Hall-Heroult process
[B] van Arkel method
[C] Mond process
[D] None of the above
Show Answer
Correct Answer: B [van Arkel method]
Notes:
van Arkel method is used for refining Titanium: This method is very useful for removing all the oxygen and nitrogen present in the form of impurity in Titanium.
8. What do we call the region of space around the nucleus where the probability of finding an electron is maximum?
[A] Shell
[B] sub-shell
[C] Orbital
[D] electron cloud
Show Answer
Correct Answer: C [Orbital]
Notes:
The region of space around the nucleus where the probability of finding an electron is maximum is called an orbital. The electron cloud is a visual model that represents all the orbitals in an atom
9. Which of the following is emitted in alpha decay?
[A] Helium nucleus
[B] Hydrogen nucleus
[C] Electrons
[D] Carbon nucleus
Show Answer
Correct Answer: A [Helium nucleus]
Notes:
In alpha decay, Helium nucleus is emitted. Alpha decay or α-decay is a type of radioactive decay in which an atomic nucleus transforms or ‘decays’ into a different atomic nucleus, with a mass number that is reduced by four and an atomic number that is reduced by two.
10. How many periods and groups are there in the Modern Periodic table?
[A] 18 groups, 7 periods
[B] 16 groups, 18 periods
[C] 7 groups, 18 periods
[D] 14 groups, 8 periods
Show Answer
Correct Answer: A [18 groups, 7 periods]
Notes:
The Modern Periodic Table has 18 vertical columns known as ‘groups’ and 7 horizontal rows known as ‘periods’.
