$\underbrace{HF\,}_{H\,-\,Bonding}\,>\,\,\underbrace{HI\,\,>\,\,HBr\,\,>\,\,HCl}_{\begin{smallmatrix}
Dipole\,\,dipole \\
attraction\,\,(V.W.forces)
\end{smallmatrix}}$
In case of same type of van der waal's forces of attraction b.pt. $\propto $ molecular mass.
કારણ : ફ્લોરીનએ ઓક્સિજન કરતાં વધુ વિદ્યુતઋણ છે.