Synthesis Chemical Reaction

Question

I'm wondering if synthesis chemical reaction, a compound is usually form by:

solid + gas = solid

solid + liquid = solid

If a solid + water (l), product is (aq)?

Is it possible for solid + solid = solid??

2Cr (s) + 3S (s) = Cr2S3 (s)

Not sure if Cr or S should be a gas to form Cr2S3??

Answer 1

Many times it depends on the temperature of the reaction.

solid + gas ==> solid is possible

solid + liquid ==> solid is possible

If a solid + H2O(l) produces a solution, then yes, product is (aq). If it produces a precipitate, then product is (s)

Is it possible for solid + solid ==> solid? Yes, it is possible, but rather rare (solventless aldol reaction e.g.)

2Cr + 3S ==> Cr2S3 takes place at high temperatures such that both Cr and S begin as solids, but S melts and then vaporizes, so I guess you could say that S should be shown as a gas (g) and Cr2S3 as solid (s) and Cr as solid (s)