In chemistry, how would somebody determine the state of matter of a compound in a chemical equation?

Question

Grade 11 Uni Chem student here with a test tomorrow.

I understand that you can use the chart to determine if polyatomic compounds are soluble or insoluble with certain elements determining whether it is (s) or (aq), but what if it isn't polyatomic?

This may be something simple the teacher quickly explained while I dozed off but I can't seem to figure out how to determine the state of something like a double displacement reaction with for example...

KI + PbNO3 ---> PbI + KNO3 (I know some elements in the example don't have the correct amount but that is irrelevant here I believe).

With a compound like this, sure I can find the solubility of PbNO3 or KNO3 to give me the state of matter for those polyatomic compounds (please correct me if that was wrong), but how would I determine whether KI or PbI are (s) or (l)?

If it's because ionic is always solid or something like that, how would I determine with 2 non metals? or even metalloids?

Sorry for the long read, my mark is pretty low and I need to understand this.

Answer 1

The simple answer to your question is SOLUBILITY RULES. If the compound is soluble it gets labeled (aq). If it is insoluble, it gets labeled (s) and if it a gas it gets labeled (g). And finally, liquids, such as H2O get labeled (l). It's as simple as that. In the example you give we have....

2KI(aq) + Pb(NO₃)₂(aq) ==> 2KNO₃(aq) + PbI₂(s) because all species are soluble except PbI₂ which is insoluble.

Does that answer your question?