Question

The halides which can react with water or undergo hydrolysis are

$PCl_{5},SiCl_{4},BCl_{3},CCl_{4}$ and $SF_{6}$

• A. $PCl_{5},SiCl_{4},BCl_{3},CCl_{4}$ and $SF_{6}$
• B. $PCl_{5},SiCl_{4},BCl_{3}$ and $CCl_{4}$
• C. $PCl_{5},SiCl_{4}$ and $BCl_{3}$
• D. $PCl_{5}$ and $SiCl_{4}$

Answer 1

Answer: (C)

Sometimes, when maximum covalency is obtained, the halides become inert to water. Thus, $SF_{6}$ is stable. This is because $SF_{6}$ is coordinately saturated and sterically hindered. Thus, $SF_{6}$ is inert to water, because of kinetic rather than thermodynamic factor. $CCl_{4}$ cannot undergo hydrolysis as carbon does not have vacant d-orbitals to extend its covalency.

Rest other $PCl _{5}, SiCl _{4}$ and $BCl _{3}$ can undergo hydrolysis as follows $PCl _{5}+4 H _{2} O \rightarrow H _{3} PO _{4}+5 H ^{+} Cl ^{-}$

$SiCl _{4}+4 H _{2} O \rightarrow Si ( OH )_{4}+4 H ^{+} Cl ^{-}$

$BCl _{3}+3 H _{2} O \rightarrow B ( OH )_{3}+3 H ^{+} Cl ^{-}$