Unit 7 The P Block Elements (Intext Questions-6)
Intext Questions
7.9 What happens when $\mathrm{PCl_5}$ is heated?
Answer All the bonds that are present in $\mathrm{PCl_5}$ are not similar. It has three equatorial and two axial bonds. The equatorial bonds are stronger than the axial ones. Therefore, when $\mathrm{PCl_5}$ is heated strongly, it decomposes to form $\mathrm{PCl_3}$. $
\mathrm{PCl_5} \xrightarrow{\text { heat }} \mathrm{PCl_3}+\mathrm{Cl_2}
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Answer
$ \begin{gathered} \mathrm{PCl_5}+\mathrm{D_2} \mathrm{O} \longrightarrow \mathrm{POCl_3}+2 \mathrm{DCl_2} \\ \mathrm{POCl_3}+3 \mathrm{D_2} \mathrm{O} \longrightarrow \mathrm{D_3} \mathrm{PO_4}+3 \mathrm{DCl} \end{gathered} $
Therefore, the net reaction can be written as
$\mathrm{PCl_5}+4 \mathrm{D_2} \mathrm{O} \longrightarrow \mathrm{D_3} \mathrm{PO_4}+5 \mathrm{DCl}$
