[phoenixcelestius]

*Sorry, NH4Cl in the title should be NH4CO3.

The problem is:
A sample of ammonium carbonate is heated.

The answer is:
(NH₄)₂CO₃   2NH₃ + CO₂ + H₂O

My answer was that NH4CO3 would decompose into (NH4)2O and CO2 according to the process of carbonate decomposition, but that's not the case. Can someone please explain why?

[SirRoderick]

The correct reaction is this: (NH4)2CO3 ---> 2NH3(g) + H2O(l) + CO2(g)

As to why yours doesn't happen...well, it just doesn't. (NH4)2O does not exist. If it were a metal carbonate you can form a metaloxide. In that case your reaction is correct.

[Schrödinger]

The oxide is formed primarily in the case of metal cations. In this case, ammonia being a quite stable compound, is formed, and not ammonium oxide (I've never heard of that before!)

[phoenixcelestius]

Thanks guys!
Another seemingly obvious question then: How do you distinguish between a stable compound and a unstable compound? Because ammonia is a "stable" base, while H2CO3 is apparently an "unstable" acid that decomposes into CO2 and H2O.

[SirRoderick]

In cases like this, it really is just something you know. Working knowledge if you will.