Structures of BeCl2 in solid state, vapour phase and at very high… — Solution | JEE Chemistry

MCQEasyJEE 2023Hybridisation

Structures of $\mathrm{BeCl_2}$ in solid state, vapour phase and at very high temperature respectively are:

Answer

Correct answer:A

Standard Method

Given: The structures of $\mathrm{BeCl_2}$ in solid state, vapour phase and at very high temperature are to be identified.

Find: The correct sequence of structures respectively.

In the solid state, $\mathrm{BeCl_2}$ exists as a polymer.

In the vapour phase, $\mathrm{BeCl_2}$ forms a chloro-bridged dimer.

At very high temperature, above $1200 \, \text{K}$ , $\mathrm{BeCl_2}$ exists as a monomer.

Therefore, the correct order is Polymeric, Dimeric, Monomeric.

The correct option is A.

Confusing the vapour phase structure with the high-temperature structure is a common mistake. Vapour phase $\mathrm{BeCl_2}$ is dimeric, whereas at very high temperature it becomes monomeric. Always distinguish ordinary vapour phase from very high temperature behaviour.
Assuming $\mathrm{BeCl_2}$ remains monomeric in all phases is incorrect. Due to electron deficiency, it forms associated structures such as polymeric and dimeric forms. Check the phase and temperature before choosing the structure.

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