Why do some reactions form solids in solution (precipitates), while others do not?

Question

i need chemistry help=]
Why do some reactions form solids in solution (precipitates), while others do not? Does the lack of a solid forming point to a non-reaction?

thanks

Answer 1

Ksp measures the tendency for a substance to ppt. Lack of a solid may or may not point to a non-reaction. You can mix a small amount of HCl solution with NaOH solution wherein Na+Cl- is formed. However, since the solubility of sodium chloride is about 35 GRAMS/L, you probably would not see a ppt unless you used some pretty conc. solutions. On the other hand, mixing one ionic soluble salt with another just leads to mixed ions of two soluble salts.

Answer 2

If the reaction is soluible then it will precipitate, if it is not soluible then no precipitate is forms. Just check out the solubility table to see what elements due and don't with each other.