Talk:Van 't Hoff factor

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Contents 1 Origin of the name 2 H2SO4 example needs to be changed 3 Too fancy 4 Too simplistic

[edit] Origin of the name

Arrgh! -- not near any Organic Chem. books. ... Did Jacobus Henricus van 't Hoff actually discover this factor? or did someone else discover it and named it after him? As it is now, I left it as the factor being named after him. Vonkje 14:27, 18 August 2005 (UTC)

[edit] H2SO4 example needs to be changed

H2SO4 dissociation is two step, assumption that 64% means 64 molecules out of 100 are completely ionized is horribly wrong. It'll all depend on concentration, but for the 0.05M solution something like 100% dissociation for the first step and 15% for the second step will be closer to reality. It'll be better to use acetic acid as an example.

[edit] Too fancy

I'm no chemist, so excuse me, but the formula is way too fancy. I was taught that Van't hoff was observed / calculate. No a - 1/ a- whatever stuff Tourskin 04:55, 10 February 2007 (UTC)

[edit] Too simplistic

The van't Hoff factors quoted for the inorganic materials assume complete dissociation in water, which only occurs in the theoretical case of infinite dilution. Using i=2 for NaCl is OK at very low concentrations, but even at 0.0010 molal, the factor is 1.97. At higher concentrations, the factor drops even more. At 1.0 molal, i = 1.81. At this concentration, assuming i = 2 yields about 10% error for any calculations.

This effect is even more pronounced for smaller ions and for ions with larger charges. For instance, MgSO₄ has i = 1.09 at 1.0 molal , even though the infinite dilution value is 2(about 80% error), just like NaCl. Even at 0.0010 molal, i = 1.82 for MgSO₄.