Mercury has a higher boiling point (357°C) than water (100°C). Use the kinetic molecular theory to explain why.

There are main ideas of the kinetic molecular theory of
gases. First is that pressure of gases is an expression of an average force that
modifies the total momentum of molecules striking the wall. the second idea is that the
temperature of a gas is an expression of the average kinetic energy of its
molecules.

This second idea can be applied also for
liquids:

`C*T =(m*v^2)/2`  where `C` is a constant 
(1)

When liquids boil the velocity of liquid's molecules
overcome the interaction intermolecular forces and thus the molecules break free into
the gas state. Assuming that both in water and in liquid mercury the strength of these
intermolecular forces is about the same, one can deduce that about the same average
velocity of their molecules will be needed at the boiling
point:

`v_("H2O") =v_("Hg")`

But since the mass of one H20 molecule is 2+16 =18 amu
(atomic mass units) and the atomic mass of Hg is 200 amu, this implies that the average
kinetic energy of water is less than the average kinetic energy of
mercury.

`m_("H2O")<m_("Hg") rArr
(m_("H2O")v_("H2O")^2)/2 < (m_("Hg")v_("Hg")^2)/2`

From this observation and (1) one can imply that at the
boiling point:

`T_(H2O) < T_(Hg)`