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1

JEE Main 2021 (Online) 27th August Morning Shift

MCQ (Single Correct Answer)
Deuterium resembles hydrogen in properties but :
A
reacts slower than hydrogen
B
reacts vigorously than hydrogen
C
reacts just as hydrogen
D
emits $$\beta$$+ particles

Explanation

The bond dissociation energy of D2 is greater than H2 and therefore D2 reacts slower than H2.
2

JEE Main 2021 (Online) 26th August Evening Shift

MCQ (Single Correct Answer)
Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R).

Assertion (A) : Heavy water is used for the study of reaction mechanism.

Reason (R) : The rate of reaction for the cleavage of O - H bond is slower than that of O - D bond.

Choose the most appropriate answer from the options given below :
A
Both (A) and (R) are true but (R) is not the true explanation of (A).
B
Both (A) and (R) are true and (R) is the true explanation of (A).
C
(A) is false but (R) is true.
D
(A) is true but (R) is false.

Explanation

D2O in used for the study of reaction mechanism. Rate of reaction for the cleavage of O-H bond > O-D bond.
3

JEE Main 2021 (Online) 26th August Morning Shift

MCQ (Single Correct Answer)
Which one of the following methods is most suitable for preparing deionized water?
A
Synthetic resin method
B
Clark's method
C
Calgon's method
D
Permutit method

Explanation

Pure demineralised (de-ionized) water free from all soluble mineral salts is obtained by passing water successively through a cation exchange (in the H+ form) and an anion exchange (in the OH$$-$$ form) resins.
4

JEE Main 2021 (Online) 26th August Morning Shift

MCQ (Single Correct Answer)
The conversion of hydroxyapatite occurs due to presence of F$$-$$ ions in water. The correct formula of hydroxyapatite is :
A
[3Ca3(PO4)2 . Ca(OH)2]
B
[3Ca(OH)2 . CaF2]
C
[Ca3(PO4)2 . CaF2]
D
[3Ca3(PO4)2 . CaF2]

Explanation

The F$$\Theta $$ ions make the enamel on teeth much harder by converting hydroxyapatite, [3Ca3(PO4)2] . Ca(OH)2], the enamel on the surface of the teeth into much harder fluroappatite. [3Ca3(PO4)2 . CaF2]

Questions Asked from Hydrogen

On those following papers in MCQ (Single Correct Answer)
Number in Brackets after Paper Indicates No. of Questions
JEE Main 2022 (Online) 24th June Evening Shift [ Memory Based ] (1)
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 (1)
JEE Main 2021 (Online) 27th August Evening Shift (1)
JEE Main 2021 (Online) 27th August Morning Shift (1)
JEE Main 2021 (Online) 26th August Evening Shift (1)
JEE Main 2021 (Online) 26th August Morning Shift (3)
JEE Main 2021 (Online) 27th July Evening Shift (3)
JEE Main 2021 (Online) 25th July Morning Shift (1)
JEE Main 2021 (Online) 22th July Evening Shift (1)
JEE Main 2021 (Online) 20th July Evening Shift (1)
JEE Main 2021 (Online) 20th July Morning Shift (1)
JEE Main 2021 (Online) 18th March Evening Shift (1)
JEE Main 2021 (Online) 18th March Morning Shift (1)
JEE Main 2021 (Online) 17th March Evening Shift (1)
JEE Main 2021 (Online) 17th March Morning Shift (1)
JEE Main 2021 (Online) 16th March Evening Shift (1)
JEE Main 2021 (Online) 16th March Morning Shift (1)
JEE Main 2021 (Online) 26th February Morning Shift (1)
JEE Main 2021 (Online) 25th February Evening Shift (1)
JEE Main 2021 (Online) 24th February Evening Shift (1)
JEE Main 2020 (Online) 6th September Evening Slot (1)
JEE Main 2020 (Online) 5th September Evening Slot (2)
JEE Main 2020 (Online) 5th September Morning Slot (1)
JEE Main 2020 (Online) 3rd September Morning Slot (1)
JEE Main 2020 (Online) 9th January Evening Slot (1)
JEE Main 2020 (Online) 7th January Evening Slot (1)
JEE Main 2020 (Online) 7th January Morning Slot (1)
JEE Main 2019 (Online) 12th April Evening Slot (1)
JEE Main 2019 (Online) 12th April Morning Slot (1)
JEE Main 2019 (Online) 10th April Evening Slot (1)
JEE Main 2019 (Online) 10th April Morning Slot (1)
JEE Main 2019 (Online) 9th April Morning Slot (1)
JEE Main 2019 (Online) 8th April Evening Slot (1)
JEE Main 2019 (Online) 8th April Morning Slot (1)
JEE Main 2019 (Online) 12th January Evening Slot (1)
JEE Main 2019 (Online) 12th January Morning Slot (1)
JEE Main 2019 (Online) 11th January Morning Slot (2)
JEE Main 2019 (Online) 10th January Morning Slot (2)
JEE Main 2019 (Online) 9th January Evening Slot (1)
JEE Main 2019 (Online) 9th January Morning Slot (1)
JEE Main 2018 (Offline) (1)
JEE Main 2016 (Online) 10th April Morning Slot (1)
JEE Main 2016 (Online) 9th April Morning Slot (1)
JEE Main 2016 (Offline) (1)
JEE Main 2015 (Offline) (2)
AIEEE 2012 (1)
AIEEE 2008 (1)
AIEEE 2003 (1)

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