JEE Main · 2021 · 20 Jul 2021 · Shift 1 · Chemical Bonding and Molecular Structure

Given below are two statements : One is labelled as Assertion A and the other is labelled as Reason

R

.
Assertion A: The dihedral angles in

H_{2} O_{2}

in gaseous phase is

90. 2^{\circ}

and in solid phase is

111. 5^{\circ}

.
Reason R: The change in dihedral angle in solid and gaseous phase is due to the difference in the intermolecular forces.
Choose the most appropriate answer from the options given below for

A

and

R

(A) $A$ is correct but $R$ is not correct.
(B)Both $A$ and $R$ are correct but $R$ is not the correct explanation of $A$ .
(C)Both $A$ and $R$ are correct and $R$ is the correct explanation of $A$
(D) $A$ is not correct but $R$ is correct.✓ Correct

Answer: (D)

Solution

In the gas phase the dihedral angle of

H_{2} O_{2}

111. 5^{\circ}

, and in the solid it closes to

90. 2^{\circ}

because hydrogen bonding to neighbouring molecules locks the two O–H bonds into a tighter arrangement. The assertion interchanges the two values, so it is wrong, while the reason correctly traces the difference to the intermolecular forces operating in the condensed phase. Assertion A is not correct but Reason R is correct.

JEE Main · 2021 · 20 Jul 2021 · Shift 1 · Single correct option

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JEE Main · 2021 · 20 Jul 2021 · Shift 1 · Chemical Bonding and Molecular Structure

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