Determine whether a solid forms when solutions containing the following salts are mixed. If so, write the ionic equation and the net ionic equation.

Question

KCl and Na2S

Answer 1

You need to study (and memorize) the solubilities of salts. Here is a simplified set of rules.
http://www.files.chem.vt.edu/RVGS/ACT/notes/solubility_rules.html