General Science Jkssb Chemistry Set 1 Mcqs (504 MCQs) | JKSSB & SSC Quiz

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jkssb chemistry set 1 mcqs

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Practice Questions

504 Total
Question 151 Discuss
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Which of the following elemental gases was discovered by Joseph Priestley in 1774 when he heated mercury oxide?

A
Silver
B
Hydrogen
C
Oxygen
D
Rhodium

Answer & Explanation

Correct Option: C

In an iconic 1774 historical experiment, the English chemist Joseph Priestley isolated oxygen gas by focusing sunlight on mercuric oxide using a magnifying glass. He originally called it 'dephlogisticated air' before Lavoisier later renamed it oxygen.
Question 152 Discuss
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Consider the statements about electrons: A. They have negative charge. B. They were discovered by J.J. Thomson. C. They orbit the nucleus.

A
Both A and C is true
B
A, B, C are true
C
Only B and C is true
D
Both A and B is true

Answer & Explanation

Correct Option: B

J.J. Thomson historically discovered the electron in 1897 using cathode ray tubes, conclusively identifying it as a fundamental subatomic particle. It is now well-established that electrons carry a negative charge and occupy complex orbital regions surrounding the dense atomic nucleus.
Question 153 Discuss
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Newlands law of octaves was only applicable upto which element?

A
Phosphorous
B
Silicon
C
Iodine
D
Calcium

Answer & Explanation

Correct Option: D

John Newlands' 'Law of Octaves,' proposed in 1865, successfully established early periodicity for lighter elements but broke down for heavier ones. Historically, his observed pattern of properties repeating every eighth element only held true up to calcium.
Question 154 Discuss
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Direct change of gas to solid without changing in to liquid is called .

A
Sublimation
B
Vaporization
C
Evaporation
D
Deposition

Answer & Explanation

Correct Option: D

Deposition, also commonly known as desublimation, is the thermodynamic phase transition where a gas transforms directly into a solid state. A classic, everyday example of deposition is the rapid formation of frost on a cold window pane in winter.
Question 155 Discuss
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Which of the following is a 's' block element?

A
Sodium
B
Carbon
C
Iron
D
Neon

Answer & Explanation

Correct Option: A

Elements located in the 's' block of the periodic table have their outermost valence electrons occupying the spherical 's' orbital. Sodium, a highly reactive alkali metal in Group 1, is an 's' block element with a single electron residing in its 3s orbital.
Question 156 Discuss
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Which of the following bacteria grow in milk and convert it to curd?

A
Salmonella typhi
B
Salmonella lactae
C
E. curdae
D
Lactic acid bacteria

Answer & Explanation

Correct Option: D

Lactic acid bacteria (LAB), such as Lactobacillus, rapidly metabolize the lactose sugars found naturally in milk and excrete lactic acid as a byproduct. This acidifiable environment historically lowers the pH, causing the milk proteins to denature and coagulate into solid curd.
Question 157 Discuss
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Which metallic element is called 'ferromagnetic' because of its strong attraction?

A
Gold
B
Molybdenum
C
Aluminium
D
Iron

Answer & Explanation

Correct Option: D

Ferromagnetism is the basic physical mechanism by which certain materials form permanent magnets or are strongly attracted to them. Iron (ferrum) is the quintessential ferromagnetic element, possessing unpaired electrons that readily align their magnetic spins parallel to an external field.
Question 158 Discuss
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Which is a colourless, odourless gas of the alkane series of hydrocarbons with a chemical formula of C3H8 ?

A
Propane
B
Butane
C
Methane
D
Ethane

Answer & Explanation

Correct Option: A

Propane (C3H8) is a three-carbon alkane gas widely utilized worldwide as a clean-burning fuel for heating and cooking. It is naturally colorless and odorless, so utility companies artificially add mercaptans to it to help people immediately detect dangerous leaks.
Question 159 Discuss
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In ethylene (C2H4), hybridisation of carbon atoms is:

A
sp2
B
sp3
C
sp
D
sp3d

Answer & Explanation

Correct Option: A

In ethylene (C2H4), a strong double bond physically forms between the two carbon atoms. To accommodate this planar geometry, each carbon atom mathematically utilizes sp2 hybridization, combining one 's' and two 'p' orbitals to form three identical sigma bonds.
Question 160 Discuss
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Which law was studied in the year 1787, in which it was said that as the volume of a gas increases its absolute temperature, if its absolute temperature decreases, then its volume will decrease?

A
Charles's law
B
Dalton's law
C
Boyle's law
D
Avogadro's law

Answer & Explanation

Correct Option: A

Formulated by Jacques Charles in an unpublished work around 1787, Charles's Law dictates that the volume of an ideal gas is directly proportional to its absolute temperature at a constant pressure. This principle historically paved the way for the invention and use of hot air balloons.
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