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 211 Discuss
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The enthalpy of formation for all elements in their standard state is:

A
unity
B
zero
C
negative
D
dependent on temperature

Answer & Explanation

Correct Option: B

By convention, the standard enthalpy of formation for a pure element in its most stable form is zero.
Question 212 Discuss
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What happens to the boiling point of water when common salt is added to it?

A
it decreases
B
it increases
C
it remains constant
D
it first increases then decreases

Answer & Explanation

Correct Option: B

Addition of a non-volatile solute causes elevation in boiling point due to a decrease in vapor pressure.
Question 213 Discuss
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Which of the following hydrocarbons is most likely to undergo an addition reaction?

A
methane
B
ethane
C
ethene
D
propane

Answer & Explanation

Correct Option: C

Unsaturated hydrocarbons like ethene (alkenes) undergo addition reactions to break their double bonds.
Question 214 Discuss
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Which of the following molecules has a linear geometry despite having lone pairs on the central atom?

A
becl2
B
co2
C
xef2
D
so2

Answer & Explanation

Correct Option: C

XeF2 has 2 bond pairs and 3 lone pairs; the lone pairs occupy equatorial positions in a trigonal bipyramidal arrangement, resulting in a linear shape.
Question 215 Discuss
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The variation of physical and chemical properties of elements with atomic weight was the basis of which periodic table?

A
moseley's periodic table
B
mendeleev's periodic table
C
newlands' octaves
D
dobereiner's triads

Answer & Explanation

Correct Option: B

Mendeleev stated that properties are a periodic function of atomic weights; modern tables use atomic number.
Question 216 Discuss
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During the electrolysis of acidified water, the volume of gas collected at the cathode is:

A
half the volume at the anode
B
double the volume at the anode
C
equal to the volume at the anode
D
four times the volume at the anode

Answer & Explanation

Correct Option: B

Water electrolysis yields 2 parts Hydrogen (at cathode) and 1 part Oxygen (at anode) by volume.
Question 217 Discuss
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Assertion (A): Glass is considered a supercooled liquid. Reason (R): Glass flows very slowly over time, similar to liquids.

A
both a and r are true and r is the correct explanation of a
B
both a and r are true but r is not the correct explanation of a
C
a is true but r is false
D
a is false but r is true

Answer & Explanation

Correct Option: A

Glass is an amorphous solid that lacks a crystal lattice and exhibits slow flow, hence termed a supercooled liquid.
Question 218 Discuss
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Which of the following indicators turns pink in a basic solution?

A
methyl orange
B
litmus paper
C
phenolphthalein
D
turmeric

Answer & Explanation

Correct Option: C

Phenolphthalein is colorless in acidic or neutral media but turns pink/magenta in alkaline conditions (pH > 8.2).
Question 219 Discuss
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In the extraction of Aluminium (Hall-Heroult process), cryolite is added to alumina to:

A
increase the melting point
B
lower the melting point and increase conductivity
C
act as an oxidizing agent
D
remove impurities of iron

Answer & Explanation

Correct Option: B

Cryolite lowers the melting point of alumina from 2050°C to approx 950°C and makes the melt more conductive.
Question 220 Discuss
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Which of the following transitions in a hydrogen atom emits a photon of the highest frequency?

A
n=2 to n=1
B
n=3 to n=2
C
n=4 to n=3
D
n=5 to n=4

Answer & Explanation

Correct Option: A

The energy gap between n=1 and n=2 is the largest in the hydrogen atom; higher energy corresponds to higher frequency.
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