$BF_3$ is used as a catalyst in several industrial processes due to its:

$NH_2^-$,$NH_3$ and $NH_4^+$ do not show similarity in the following:

In the electronic structure of $H_2SO_4$,the total number of unshared electrons is

The correct order of strength of $\pi-$ bond$(s)$ is:
$I$. $BO_3^{-3} < CO_3^{-2} < NO_3^{-}$
$II$. $ClO_4^{-} > SO_4^{-2} > PO_4^{-3}$
$III$. $BF_3 > BCl_3 > BBr_3$
$IV$. $AlCl_3 < BCl_3$

Assertion : Bond angle of $H_2S$ is smaller than $H_2O$.
Reason : Electronegativity of the central atom increases,bond angle decreases.

Considering ethene molecule,which of the following statements is/are correct?
$I$. $C-C$ bond is formed by overlapping of $sp^2-sp^2$ hybrid orbitals.
$II$. $C-H$ bond is formed by overlapping of $sp^2-s$ orbitals.
$III$. $p\pi-p\pi$ bond is present.
$IV$. $H-C-H$ bond angle is greater than $H-C-C$ bond angle.
$V$. Nodal plane of $\pi$ bond and molecular plane are same.