Question

Which of the following statement(s) is/are correct for $PC{l}_5$?

• A. $P$ atom is $s{p}^{3}d$ - hybridized and has trigonal bipyramidal geometry
• B. It acts as a Lewis acid
• C. On hydrolysis it forms phosphoric acid
• D. Axial $Cl$ atoms are closer to equatorial $Cl$ atoms

Answer 1

Answer: (A), (B), (C)

On hydrolysis it forms phosphoric acid

In the gaseous state, $PC{l}_5$ exists as a trigonal bipyramidal molecule.

The equatorial bonds are shorter than the axial bonds. While the two axial bonds are 214 pm, the three equivalent equatorial bonds are 202 pm.

So the axial Chlorine atoms are more susceptible to be removed than the three equatorial ones!

On partial hydrolysis,
$PC{l}_5+H_{2}O⟶POC{l}_3+2HCl$

In hot water, hydrolysis proceeds completely to orthophosphoric acid:
$PC{l}_5+4H_{2}O⟶H_{3}P{O}_4+5HCl$

Phosphorus pentachloride is a Lewis acid (an electrophile):
$RCOOH+PC{l}_5⟶RCOCl+HCl+POC{l}_3$