Bezaleel - 5-7-2013 at 07:57
I'm looking for a methatesis reaction to produce a solution of CsF. Of course, CsF could be produced from HF and a suitable Cs-salt, but I do not want
to use HF.
Now, BaF and BaSO4 are both sparingly soluble, their respective solubilities being 0.16 g/100ml and 0.00024 g/100ml @20C. The absolute enthalpies of
formation @298K are -1207.1 kJ/mol and -1473.2 kJ/mol respectively.
Would a methatesis reaction of BaF and Cs2SO4 in water work, and run to more or less completeness (say 99%)? Would heating be necessary, or will the
release of some 250kJ/mol be enough to drive the formation of BaSO4?
blogfast25 - 5-7-2013 at 08:28
With a solubility product of 10<sup>-10</sup> BaSO4 really can be classed more or less as 'insoluble'. BaF2 is only sparingly soluble in
water. CsF appears to be very highly soluble in water, as is Cs2SO4.
The difference in solubility between BaF2 and BaSO4 means that in the presence of sulphate ions and water even solid BaF2 will probably convert to
BaSO4, more or less completely. But the resulting CsF solution will be slightly contaminated with BaSO4. And BaSO4 has a tendency for occlusion.
To speed things up, keep hot and stir for considerable time. After cooling, test for sulphates.
Consider also 2 CsOH + NH4HF2 === > 2 CsF + NH3 + 2 H2O
Ammonium bifluoride is much safer to handle than HF.
[Edited on 5-7-2013 by blogfast25]