Explanation

(a)
$Cl - P - Cl$ bond angles in $PCl_{5}$ molecule are $120{^\circ}$ and $90{^\circ}$. $PCl_{5}$, having $sp^{3}d$ hybridised P atom (trigonal bipyramidal geometry) has two types of bonds; axial and equatorial. The two types of bond have different bond lengths 1, 2, 3 and 4 equatorial bonds and 4, 5 axial bonds.
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