Question

Phosphorus pentachloride

• A. On hydrolysis gives an oxo acid of phosphorus which is tribasic
• B. On hydrolysis gives an oxo acid of phosphorus which is a good reducing agent
• C. Has all the five equivalent bonds
• D. Exists as an ionic solid in which cation has octahedral structure and anion has tetrahedral structure

Answer 1

Answer: (A)

(a) Phosphorous pentachloride $\left(PC{l}_5\right)$ has a trigonal bipyramidal structure. Here, the five bonds are not of equal lengths as the axial bonds are slightly longer than the equatorial bonds.

(b) $PC{l}_5$ solid exists as ${\left[PC{l}_4\right]}^{+}$ and ${\left[PC{l}_6\right]}^{-}$ and they have tetrahedral and octahedral structures respectively.

(c) On hydrolysis, $PC{l}_5$ gives $H_{3}P{O}_4$ which is tribasic.

$PC{l}_5+4H_{2}O\to H_{3}P{O}_4+5HCl$

In $H_{3}P{O}_4,P$ is in its $+5$ oxidation state. So it is in its highest oxidation state and hence is not a good reducing agent.