Total number of molecules which have cation-anion pair out of $I_{2(s)}$,dry ice $(CO_{2(s)})$,$PCl_{5(s)}$,$N_2O_{5(s)}$,$PBr_{5(g)}$ is

Graphite is a soft solid lubricant and is extremely difficult to melt. What is the reason for this behavior of graphite?

$PBr_{5(s)} \rightarrow PBr_{4}^{+} + Br^{-}$
$Br^{-} + Br_2 \rightarrow Br_{3}^{-}$
Which of the following forces is responsible for the interaction of $X^{-}$ and $X_2$ to form a coordinate bond between $X^{-}$ and $X_2$?

Intermolecular forces are forces of attraction and repulsion between interacting particles that will include :
$A$. dipole-dipole forces $B$. dipole-induced dipole forces $C$. hydrogen bonding $D$. covalent bonding $E$. dispersion forces
Choose the most appropriate answer from the options given below :

Suggest the most important type of intermolecular attractive interaction in the following pairs.
$(i)$ $n$-hexane and $n$-octane
$(ii)$ $I_{2}$ and $CCl_{4}$
$(iii)$ $NaClO_{4}$ and water
$(iv)$ methanol and acetone
$(v)$ acetonitrile $(CH_{3}CN)$ and acetone $(C_{3}H_{6}O)$

Graphite is a soft solid lubricant extremely difficult to melt. The reason for this anomalous behaviour is that graphite