On the transformation $PCl_5 \to PCl_6^-$,what changes will take place?

What is the meaning of hybridization of atomic orbitals?

$KI + MnO_2 + H_2SO_4 \to$ Vapours $(B) +$ other products
Vapours $(B) + K_2S_2O_8 \to (C) + (D)$
$(D) \xrightarrow{(B)}$ Brown $(E)$
Hybridisation of central atom in $(E)$ is

Describe hybridization in the case of $PCl_5$ and $SF_6$. The axial bonds are longer as compared to equatorial bonds in $PCl_5$ whereas in $SF_6$ both axial bonds and equatorial bonds have the same bond length. Explain.

Which of the following statements is true regarding the $PCl_5$ molecule?
$(i)$ The two axial $P-Cl$ bonds in $PCl_5$ are longer than the three equatorial bonds.
$(ii)$ The axial bonds in $PCl_5$ are stronger than equatorial bonds.
$(iii)$ The axial bonds in $PCl_5$ are more stable than equatorial bonds.
$(iv)$ All five bonds in $PCl_5$ molecule are equivalent.

What is the hybridization state of the chlorine atom in $ClO_4^-$,$ClO_3^-$,and $ClO_2^-$ ions,respectively?