Question

Assertion: Bond lengths of P—Cl bonds in gaseous $PC{I}_5$ and solid $PC{I}_5$ are not equal.
Reason: Because in solid state two $PC{I}_5$ molecules are associated.

• A. If both assertion and reason are true and reason is the correct explanation of assertion.
• B. If both assertion and reason are true but reason is not the correct explanation of assertion.
• C. If assertion is true but reason is false.
• D. If both assertion and reason are false.

Answer 1

Answer: (A)

As in solid state, $PC{l}_5$ exists as an ionic solid ${\left[PC{l}_4\right]}^{+}{\left[PC{l}_6\right]}^{-}$ in which the cation, ${\left[PC{l}_4\right]}^{+}$ is tetrahedral and the anion, ${\left[PC{l}_6\right]}^{-}$ is octahedral.

$PC{l}_5$ in gaseous state has trigonal bipyramidal structure in which three equatorial bonds are equivalent, while the two axial bonds are longer than equatorial bonds due to more bond pair repulsion.