What type of bonds are present in molecular crystals?

What is the dependence of interaction energy on the distance $(r)$ between molecules for the following forces?
$(i)$ London forces
$(ii)$ Dipole-dipole forces (stationary)
$(iii)$ Dipole-induced dipole forces

$Na_2SO_4$ is water soluble but $BaSO_4$ is insoluble because

$\Delta_r H$ of which reaction correctly represents the lattice enthalpy of $NaCl_{(s)}$?

$I_2$ molecules are held in the solid lattice by $...................$

Dipole-induced dipole interactions are present in which of the following pairs?