van't Hoff factor -- i

[datdat]

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when it comes to colligative properties calculation we should know i as in
pi = i MRT....

but I'm not sure how I could figure it out for a certain molecules

for example i for NaCl is 4 (kbb p.909 i think it's because they are dealing with 2M in 1 L...i guess...)

is there any way I can figure that i out for different molecule?

or should I memorize for some compound? if so what are they that I need to memorize?

 

[alanan84]

i is the # of moles the molecule dissociates into. So for NaCl, i is actually 2. For BaCl2, i is 3 and so on. For glucose, i is one because it doesn't dissociate into ions in solution.

 

[saDDS]

quick question...i know we use i for the colligative properties, but we do not use it for vapor pressure correct? its just VP = VP (pure) * mole fraction