how do you tell whether or not a reaction is a precipitation based on ionic compounds?

Consider precipitation reaction. First of all, you have to confirm that both reactants are soluble in water, i.e. two aqueous solution.

Precipitation reaction is double displacement, or simply, interchanging the anions and cations to give two ionic compounds. Reaction occurs if at least one of the ionic compounds is insoluble in water.

For example, when mixing cobalt chloride and copper sulfate, the expected products of double displacement are cobalt sulfate and copper chloride. There is no precipitate because both cobalt sulfate and copper chloride are soluble in water.

micatkie said:


"Reaction occurs if at least one of the ionic compounds is insoluble in water."

But how do you do that?

1) You look up each product in a solubility chart (also called solubility table or solubility rules). Here is an example:

http://intro.chem.okstate.edu/1515SP01/Database/Solub.html

2) You can also look up each compound on the Internet. For example:

https://www.google.com/search?client=firefox-b-1-d&q=Cucl2+ksp

I included Ksp in the search because that is a way to help determine if a compound is soluble. If it has a Ksp value, then that means it is insoluble. You cannot locate a Ksp value for CuCl2 because it is a soluble compound.