How could you use a precipitation reaction to separate the following pair of cations: K^+ and Hg2 ^2+? (write the formula and net formula for each reactant)?

Question

How could you use a precipitation reaction to separate the following pair of cations: K^+ and Hg2 ^2+? (write the formula and net formula for each reactant)?  
The answer is 
Hg2 ^2+ (aq) + 2Cl- (aq) = HgCl2(s) but how do I work it out?

DrBob222 · Accepted Answer

Are you asking how you know to write this equation. You must know solubility rules. Almost all (but not all) K compounds are soluble. Hg(I) chlorides are not soluble. If you don't have the solubility rules memorized here is a simplified set for you to peruse.
http://www.files.chem.vt.edu/RVGS/ACT/notes/solubility_rules.html