[Nedgy]

A learnt a definition that said "A precipitation reaction is a type of chemical reaction, in which two soluble salts in an aqueous solution combine and one of the products in an insoluble salt called a precipitate". Thought it was neat, then I was reading an article and it said this was a precipitation reaction:

2AgNO3(aq) + Cu(s) →Cu(NO3)2(aq) + 2Ag(s)

According to the above definition, we need two soluble salts, copper is not a soluble salt (right?) I mean it's solid for one thing and I learnt that a salt is an ionic compound that consists of a cation and an anion which obviously, pure copper is not.

So how exactly can you categorizes something as a precipitation reaction, thank you.

[Borek]

I don't like the definition you have listed, whoever coined it lacked imagination. It tries to be precise but narrows the scope. Say, you mix AgNO₃ and HCl precipitating AgCl - you haven't mixed two salts, yet this is a perfectly valid example of precipitation reaction. Same when mixing FeCl₃ with NaOH, you end with the precipitated Fe(OH)₃. Thing that is important is that you mix two solutions and something precipitates out.

I am not sure I would classify the reaction between Ag⁺ and Cu(s) as a precipitation reaction. You are displacing one solid with another. From what I understand some do classify it this way. As far as I am aware there is no one, generally accepted definition of what the precipitation reaction is and what classifies as one, so probably there is no simple yes/no answer here.

[Nedgy]

Great answer and I think I understand, I've asked around about it seems that's the consensus is, you can consider something a precipitation reaction if over the course of your chemical reaction, a precipitate was produced, but there's no exclusive set rules so take it with a grain of salt, am I correct in saying that?

[Borek]

Great answer and I think I understand, I've asked around about it seems that's the consensus is, you can consider something a precipitation reaction if over the course of your chemical reaction, a precipitate was produced, but there's no exclusive set rules so take it with a grain of salt, am I correct in saying that?

Yes, that's another way of putting it.