What is the bond angle observed in the $H-C-H$ bond of ethane (in $^{\circ}$)?

What type of orbital hybridisation is considered on $P$ in $PCl_5$?

The types of hybridisation on the five carbon atoms from left to right in $pent-1-en-4-yne$ are

"Hybridisation of central atom does not always change due to back bonding". This statement is valid for which of the following compounds?
$(i)$ $CCl_3^-$ $(ii)$ $CCl_2$ $(iii)$ $(SiH_3)_2O$ $(iv)$ $N(SiH_3)_3$

The state of hybridization of the central atom is not the same as in the others.

Order of the bond strength of $C-H$ bonds involving $sp, sp^2$ and $sp^3$ hybridized carbon atoms is