Subject: why does carbonic acid decompose when it is created with acetic acid?

       I recently did an experiment in class, where I placed an egg 
(hard boiled) into a small beaker of vinegar (acetic acid). according 
to the chemical equation the reaction of the acetic acid and calcium 
carbonate of the egg shell produces calcium acetate and carbonic acid, 
which then decomposes into water and carbon dioxide. 
       what I have been trying to prove is why the acid decomposes. my 
theory is that the energy given off by the spontaneous reaction of the 
calcium carbonate and acetic acid is enough to raise the produced 
carbonic acid to its activation energy for decomposing. first, is this 
correct? second, is this incorrect because the hydrogen in the 
carbonic acid is actually in the form of hyronium ions? thirdly, if 
that is incorrect am I even close? thank you for your time.

Ben Trubits  

Re: why does carbonic acid decompose when it is created with acetic acid?