J.R. S. answered • 03/16/18
Tutor
5.0
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Ph.D. in Biochemistry--University Professor--Chemistry Tutor
The only way to know this is to know and understand solubility rules. There are certain compounds that are not soluble to any appreciable extent in water, and these will form a precipitate. For example, silver chloride (AgCl) is not soluble, so in the following reaction it will form a precipitate: AgNO3(aq) + NaCl(aq) ==> AgCl(s) + NaNO3(aq). So, you just have to know (or look up) the solubility rules and the solubility of various salts in order to KNOW which will precipitate.
