[moze]

http://i.imgur.com/XdgdXbF.png?1
Not sure about quite a few bits of this question... here's what I've got so far

i) nothing

ii) Ideal solution - molecules must be similar in size & shape, molecules must be similar in chemical nature so that they have similar intermolecular forces

iii) Ptotal = Pa + Pb  where Pa = xa*Pa*   (Pa* pure component vapour pressure, xa mole fraction, Pa partial vapour pressure of a)

iv) Use some form of Clapeyron equation? dH / TdV = dP / dT ? (I'm sure this would be do-able if I could answer the earlier parts.. maybe)

[mjc123]

Heard of the Clausius-Clapeyron equation?

[MrTeo]

i) mjc123 already gave you the hint for this.

ii) Seems correct to me. I quite like the fact that you mentioned the shape, as, even with comparable (with the ones in the pure solute/solvent) interaction between the solute and the solvent, the shape might cause even drastic changes in packing and induce reorganization (thus, no ideality).

iii) Sounds good. You could also mention that Raoult's law allows you to write an alternative (and more operative, if you want) definition of ideal solution. An ideal solution is one that follows Raoult's law in the whole concentration range (so from x_A 0 to 1).

iv) What is the ideal mixing enthalpy? And the ideal mixing entropy?