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 $\left( PCl _{5}\right)$ 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) $PCl _{5}$ solid exists as $\left[ PCl _{4}\right]^{+}$ and $\left[ PCl _{6}\right]^-$ and they have tetrahedral and octahedral structures respectively.

(c) On hydrolysis, $PCl _{5}$ gives $H _{3} PO _{4}$ which is tribasic.

$PCl _{5}+4 H _{2} O \rightarrow H _{3} PO _{4}+5 HCl$

In $H _{3} PO _{4}, P$ is in its $+5$ oxidation state. So it is in its highest oxidation state and hence is not a good reducing agent.