Q.Describe the structure of $\text{PCl}_3$ and write the equation for its hydrolysis.

[!TLDR] PCl3 is trigonal pyramidal (sp3 P, one lone pair) and hydrolyses completely to phosphorous acid and HCl. [!ANSWER] PCl3 is trigonal pyramidal; $\text{PCl}_3 …

$\text{PCl}_3$, prepared by passing limited chlorine over gently heated white phosphorus ($\text{P}_4 + 6\text{Cl}_2 \rightarrow 4\text{PCl}_3$), is structurally directly analogous to $\text{NCl}_3$ and $\text{NH}_3$: phosphorus is $sp^3$ hybridised, forming three $\sigma$ bonds to the three chlorine atoms, with the fourth hybrid orbital holding the lone pair, giving a trigonal pyramidal shape (Cl-P-Cl angle around $100^\circ$). $\text{PCl}_3$ fumes visibly in moist air and is completely and readily hydrolysed by water, giving phosphorous acid and hydrochloric acid: $$\text{PCl}_3 + …

State the shape by the same sp3/one-lone-pair logic as NH3/NCl3, then write the balanced hydrolysis equation, noting …

Writing the hydrolysis product as H3PO4 (phosphoric acid) instead of H3PO3 (phosphorous acid) -- phosphorus stays in the +3 stat …