Question

The main reason the $SiCl_4$ is easily hydrolysed as compared to $CCl_4$ is that

• A. Si - Cl bond is weaker than C - Cl bond
• B. $SiCl_4$ can form hydrogen bonds
• C. $SiCl_4$ is covalent
• D. Si can extend its coordination number beyond four

Answer 1

Answer: (D)

Si can extend its coordination number beyond four

Answer 2

The main reason that $SiCl _{4}$ is easily hydrolysed as compared to $CCl _{4}$ is that $Si$ can extend its coord�nation number beyond four because it has vacant $d$-orbital. On the other hand, carbon has no $d$-orbital thus, it cannot extend its coordination number beyond four, so its halides are not attacked (hydrolysed) by water. The vacant $d$-orbitals of $Si$ can coordinate with water molecules and hence their halides are hydrolysed by water.
The hydrolysis of $SiCl _{4}$ occurs due to coordination of - OH with empty $3 d$-orbitals of Si-atom of $SiCl _{4}$ molecule.