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KCET 2020 Chemistry Solved Paper

Question : 4 of 60

Marks: +1, -0

Phosphorous pentachloride

Has all the five equivalent bonds
Exist as an ionic solid in which the cation has an octahedral structure and the anion has a tetrahedral structure
On hydrolysis gives an oxo acid of phosphorous which is tribasic
On hydrolysis gives an oxo acid of phosphorous which is a good reducing agent

Solution:

a. Phosphorous pentachloride (

\mathrm{PCl}_5

) has a trigonal bipyramidal structure. Here, the five bonds are not of equal lengths as the axial bonds are slightly longer than the equatorial bonds.

\mathrm{PCl}_5

solid exists as

[\mathrm{PCl}_4]^{+}

and

[\mathrm{PCl}_6]^{-}

and they have tetrahedral and octahedral structures respectively.

c. On hydrolysis,

\mathrm{PCl}_5

gives

\mathrm{H}_{3}\mathrm{PO}_{4}

which is tribasic.

\mathrm{PCl}_5 + 4 \mathrm{H}_{2}\mathrm{O} \rightarrow \mathrm{H}_{3}\mathrm{PO}_{4} + 5 \mathrm{HCl}

d. In

\mathrm{H}_{3}\mathrm{PO}_{4}, \mathrm{P}

is in its

+5

oxidation state. So it is in its highest oxidation state and hence is not a good reducing agent.

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