(1) (a) When boiling, a substance undergoes a phase transition from liquid to vapour. (i) Compare the molecular structure and interactions in liquids and gases. What do they have in common, and in what do they differ? Indicate for both the vaporisation enthalpy
\Delta _(vap )H
and the vaporisation entropy
\Delta _(vap )S
whether they are positive or negative. Explain. (3 marks) At 1 atm, water boils at
100\deg C
. The mass density of the liquid water at this temperature is
0.958kgdm^(-3)
. (ii) Calculate the concentration, that is the number of moles (mol) water per liter
(dm^(3))
, of liquid water at
100\deg C
. Give your answer to 3 significant figures. (2 marks) (iii) Calculate the concentration of water in a bubble of water vapour under these conditions. Give your answer in units of
moldm^(-3)
and to 3 significant figures. Assume the vapour behaves as an ideal gas. (2 marks)