I did a project for lab chemistry where my aim was to see which substance, from a selection of 4 chlorides, recrystallises from a solution to form the most crystals. The 4 chlorides were KCl, NaCl, MgCl2 and CaCl2.

Question

KCl and NaCl didn't form any crystals, they formed a saturated solution whereas MgCl2 and CaCl2 formed crystals. It seems as if the charges on the positve ion of the chloride are important here; but why? How do I explain my results? Conclusion??

Answer 1

Since you've posted this numerous times, I'm responding but I don't have a real answer for you.
First, I don't think four sample runs are enough to make profound conclusions. Second, I think the NaCl and KCl would have crystallized if they stood long enough because as the water evaporates some of the salt MUST come out of solution.
Third, crystal formation often depends upon the nature of the material as well as a seed to get it started.
http://www.rpi.edu/dept/chem-eng/Biotech-Environ/DOWNSTREAM/form.htm