Structure of $BeCl_2$ in solid state,vapour phase and at very high temperature respectively are :-

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 $(C_{3}H_{6}O)$

Which set of compounds in the following pairs of ionic compounds has the higher lattice energy?
$(i) \, KCl$ and $MgO$
$(ii) \, LiF$ and $LiBr$
$(iii) \, Mg_3N_2$ and $NaCl$

If the value of ionic radius ratio $\left( \frac{r_c}{r_a} \right)$ is $0.52$ in an ionic compound,the geometrical arrangement of ions in the crystal is:

What are the intermolecular forces present between $H_2$ and $HCl$ molecules? Why?

Dry ice is an example of