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NTA Abhyas 2020

Exam: NTA Abhyas
Year: 2020
Subject: Chemistry
Chapter: p Block Elements (Group 13 & 14)

NTA Abhyas 2020 · Chemistry · p Block Elements (Group 13 & 14)

AlC l _ 3 forms dimer in vapour phase but BC l _ 3 does not because

AlC{l}_{3}

forms dimer in vapour phase but

BC{l}_{3}

does not because

Options

AIn $Al$ there are vacant d orbitals in which it accommodates lone pair from chlorine atoms
BIn ${BCl}_{3}$ there is back bonding
CThere is hydrogen bonding in between two $AlC{l}_{3}$ molecules in vapour phase
DNone of the above

Correct answer

A. In $Al$ there are vacant d orbitals in which it accommodates lone pair from chlorine atoms

Step-by-step solution

The formation of stronger backbond (3p \to 2p

overlap in

BC{l}_{3}

and weaker 3p \to 3p

overlap in

AlC{l}_{3}

) reduces the electron deficiency of the central atom and thus dimerisation tendency is reduced. So

AlC{l}_{3}

can form a dimer but

B{F}_{3}

and

BC{l}_{3}

cannot.

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