I have a question about solubility rules and net ionic equations

Question

so for example :
CuSO4+Ba(NO3)2----->BaSO4+Cu(NO3)2 Okay so I know BaSO4 is insoluble while Cu(NO3)is solulable, that means BaSO4 will have a precipitate while Cu(NO3) doesn't. So does that mean the overall equation will have a reaction because one of the two compounds has a precipitate?
IN other words in an equation if both compounds have a precipitate and are insoluble will there be a reaction? what if it's only one compound with a precipitate/is insoluble like the example that I gave above, will there be a reaction? what if they both are soluble/don't have a precipitate will there be a reaction?

Thanks!

Answer 1

The rules I remember for reactions:
1. A rxn will occur if a (a meaning one) ppt forms. It goes without saying that if two ppts form there will be a reaction also.
Your rxn is an example.

2. A rxn will occur if a gas is formed. Example:
2Na + H2O ==> 2NaOH + H2

3. A rxn will occur if a weak electrolyte is formed. Example:
NaOH + HCl ==> NaCl + H2O (H2O is the weak electrolyte; i.e., slightly ionized).

4. Redox reactions occur if the voltage between the two is positive.

Here is why those rules apply. Reactions occur if anything happens to force the equilibrium of the reaction to the right producing more products.

1. Formation of a ppt. The ppt essentially leaves the field of reaction (because it's insoluble), the reverse reaction can't take place because the ppt is not soluble so reactants continue to form ppt until all of the reactants are used. Most of the ppt reactions take place at close to 100%.

2. A gas is formed. This is another case where the gas leaves the field of reaction; therefore, no reverse reaction can take place and the reactants continue to produce more products until all of the reactants are gone.

3. A weak electrolyte is formed. Another case in which the weak electrolyte leaves the field of reaction and the reverse reaction can't continue as well as the forward reaction.

4. Redox. These reactions have their own rules.

Hope this helps.