Explain the molecular structure and properties of phosphorus pentachloride $(PCl_5)$.

(N/A) Structure: Phosphorus pentachloride $(PCl_5)$ has a trigonal bipyramidal geometry in gaseous and liquid phases. The phosphorus atom undergoes $sp^3d$ hybridization.
In $PCl_5$,the three equatorial $P-Cl$ bonds are equivalent,while the two axial $P-Cl$ bonds are longer than the equatorial bonds. This is because the axial bond pairs experience greater repulsion from the equatorial bond pairs compared to the repulsion between equatorial bond pairs themselves.
Properties of $PCl_5$:
$1$. $PCl_5$ is a yellowish-white powder. In moist air,it hydrolyzes to give phosphorus oxychloride $(POCl_3)$ and finally phosphoric acid $(H_3PO_4)$:
$PCl_5 + H_2O \rightarrow POCl_3 + 2HCl$
$POCl_3 + 3H_2O \rightarrow H_3PO_4 + 3HCl$
$2$. When heated,it sublimes,but on strong heating,it decomposes:
$PCl_5 \xrightarrow{\Delta} PCl_3 + Cl_2$
$3$. It reacts with organic compounds containing the $-OH$ group,converting them into chloro derivatives:
$C_2H_5OH + PCl_5 \rightarrow C_2H_5Cl + POCl_3 + HCl$
$CH_3COOH + PCl_5 \rightarrow CH_3COCl + POCl_3 + HCl$
$4$. Finely divided metals,upon heating with $PCl_5$,yield their corresponding chlorides:
$2Ag + PCl_5 \rightarrow 2AgCl + PCl_3$
$Sn + 2PCl_5 \rightarrow SnCl_4 + 2PCl_3$