Hi,
I have mixed 0.5 L of H2O (T= 30°C) with 1 kg of Carnallite (containing 140 g NaCl, 180 g KCl, 270 g MgCl2 and 20 g CaCl2). Since that solubility of NaCl, KCl, MgCl2 and CaCl2 at 30°C are 36, 37, 56 and 100 g in 100 g H2O, respectively, How much of these salts dissolve in water and how much stays in the solid phase?
By simple calculations, the 0.5 L is about 500 g (Assuming the density of water = 1 g/ml). So you can dissove 5 times the quantities that you have mentioned in your question:
1- 36x5 = 180 g NaCl, since you have only 140 g NaCl, all NaCl will dissolve.(If it is alone)
2- 37x5 = 185 g KCl, so all KCl will dissolve also. .(If it is alone)
3- 56 x 5 = 280 g MgCl2, so all MgCl2 will dissove also..(If it is alone)
4- 100 x 5 = 500 g CaCl2, so all CaCl2 will dissove also. .(If it is alone)
But if all of them togother, the most one that is soluble it dissolves first.
So,
1- All 20 g CaCl2 will dissolve completely and this represents (20/500) x 100% =4.00% CaCl2 of the total solubility
2- (270/280) x 100% = 96.43%.MgCl2 of the total solubility.
3- If we add them together 4.00 + 96.43 we will get 100.43%, so there will be some of the MgCl2 will not dissolve which is equal to 0.43% x 280 = 1.20 g
3- So all CaCl2 will dissolve and 268.80 g of MgCl2 will dissolve.
4- All the quantity of KCl and NaCl will precipitate.
Thank you for your complete answer
Is it possible that these salts are dissolved simultaneously and in proportion to their solubility in water, or the salt that is more solubilized, it is first dissolved, and then the next salt is solved ?!
How much should be the solubility of salts in water, so that they can not be solved simultaneously?
I suggest this work:
Article Thermodynamic modeling of KCl + H2O and KCl + NaCl + H2O sys...
Sadegh Yousefi
According to the solubility rules and my knowledge, the one that is more soluble is dissolve first and the least soluble salt will remain as is and will precipitate.
Practically I do not know what are the results.
You can experimentaly find the results, by filtering the solution and anlyze the precipitate. If you find that you have too much Mg+2 and Ca+2 ions using Hardnes of water test (Titration method), so my suggestion is wrong. Or you can analyze the filtrate solution and if you have mostly Na+ and K+ and very little Mg+2 and Ca+2, my suggestion will be correct.
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