Consider the following sequences of molecules and their associated...

Statement (I): The dipole moment of chloromethanes decreases as the number of chlorine atoms increases due to the vector addition of individual bond moments. The experimental values are $\mathrm{CH}_3\mathrm{Cl}$ ($1.87$ D) $\gt$ $\mathrm{CH}_2\mathrm{Cl}_2$ ($1.60$ D) $\gt$ $\mathrm{CHCl}_3$ ($1.04$ D). This sequence is correct.

Statement (II): The bond angle of group 16 hydrides decreases down the group. As the electronegativity of the central atom decreases, the bond pairs move further away from the central atom, decreasing the bond pair-bond pair repulsion. The correct order is $\mathrm{H}_2\mathrm{O}$ ($104.5^\circ$) $\gt$ $\mathrm{H}_2\mathrm{S}$ ($92.1^\circ$) $\gt$ $\mathrm{H}_2\mathrm{Te}$ ($90^\circ$). This sequence is incorrect.

Statement (III): The bond order of $\mathrm{CO}$ is $3$, $\mathrm{CO}_2$ is $2$, and $\mathrm{CO}_3^{2-}$ is $1.33$. Since bond length is inversely proportional to bond order, the correct order of $\mathrm{C}-\mathrm{O}$ bond length is $\mathrm{CO}_3^{2-} \gt \mathrm{CO}_2 \gt \mathrm{CO}$. This sequence is incorrect.

Statement (IV): The total number of electrons in $\mathrm{NO}^+$, $\mathrm{NO}$, and $\mathrm{NO}^-$ are $14$, $15$, and $16$ respectively. According to molecular orbital theory, their bond orders are $3$, $2.5$, and $2$ respectively. The correct order of bond order is $\mathrm{NO}^+ \gt \mathrm{NO} \gt \mathrm{NO}^-$. This sequence is correct.

Therefore, only sequences I and IV are correct.

Answer: I and IV only