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1

JEE Main 2021 (Online) 27th August Evening Shift

MCQ (Single Correct Answer)
The correct order of ionic radii for the ions, P3$$-$$, S2$$-$$, Ca2+, K+, Cl$$-$$ is :
A
P3$$-$$ > S2$$-$$ > Cl$$-$$ > K+ > Ca2+
B
Cl$$-$$ > S2$$-$$ > P3$$-$$ > Ca2+ > K+
C
P3$$-$$ > S2$$-$$ > Cl$$-$$ > Ca2+ > K+
D
K+ > Ca2+ > P3$$-$$ > S2$$-$$ > Cl$$-$$

Explanation

P3$$-$$ > S2$$-$$ > Cl$$-$$ > K+ > Ca2+ (Correct order of ionic radii)

all the given species are isoelectronic species. In isoelectronic species size increases with increase of negative charge and size decreases with increase in positive charge.
2

JEE Main 2021 (Online) 27th August Evening Shift

MCQ (Single Correct Answer)
Choose the correct statement from the following :
A
The standard enthalpy of formation for alkali metal bromides becomes less negative on descending the group.
B
The low solubility of CsI in water is due to its high lattice enthalpy.
C
Among the alkali metal halides, LiF is least soluble in water.
D
LiF has least negative standard enthalpy of formation among alkali metal fluorides.

Explanation

a. Standard enthalpy of formation for alkali metal bromides becomes more negative on descending down the group.

b. In case of CsI, lattice energy is less, but Cs+ is having less hydration enthalpy due to which it is less soluble in water.

c. For alkali metal fluorides, the solubility in water increases from lithium to caesium. LiF is least soluble in water.

d. Standard enthalpy of formation for LiF is most negative among alkali metal fluorides.
3

JEE Main 2021 (Online) 27th August Morning Shift

MCQ (Single Correct Answer)
In which one of the following molecules strongest back donation of an electron pair from halide to boron is expected?
A
BCl3
B
BF3
C
BBr3
D
BI3

Explanation

Type of back bonding

$$\matrix{ {B{F_3}} & {BCl} & {BB{r_3}} & {B{I_3}} \cr {(2p\pi - 2p\pi )} & {(2p\pi - 3p\pi )} & {(2p\pi - 4p\pi )} & {(2p\pi - 5p\pi )} \cr } $$

Therefore back bonding strength is as follows

BF3 > BCl > BBr3 > BI3
4

JEE Main 2021 (Online) 26th August Evening Shift

MCQ (Single Correct Answer)
Chalcogen group elements are :
A
Se, Tb and Pu.
B
Se, Te and Po.
C
S, Te and Pm.
D
O, Ti and Po.

Explanation

Group 16/oxygen family is known as Chalcogens the members are O, S, Se, Te, Po

Questions Asked from Periodic Table & Periodicity

On those following papers in MCQ (Single Correct Answer)
Number in Brackets after Paper Indicates No. of Questions
JEE Main 2022 (Online) 24th June Morning Shift [ Memory Based ] (1)
JEE Main 2021 (Online) 1st September Evening Shift (1)
JEE Main 2021 (Online) 31st August Evening Shift (2)
JEE Main 2021 (Online) 31st August Morning Shift (2)
JEE Main 2021 (Online) 27th August Evening Shift (3)
JEE Main 2021 (Online) 27th August Morning Shift (1)
JEE Main 2021 (Online) 26th August Evening Shift (2)
JEE Main 2021 (Online) 27th July Evening Shift (1)
JEE Main 2021 (Online) 25th July Evening Shift (1)
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JEE Main 2021 (Online) 22th July Evening Shift (2)
JEE Main 2021 (Online) 18th March Evening Shift (1)
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JEE Main 2021 (Online) 16th March Morning Shift (1)
JEE Main 2021 (Online) 26th February Evening Shift (1)
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JEE Main 2021 (Online) 25th February Evening Shift (1)
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JEE Main 2020 (Online) 5th September Evening Slot (1)
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