Okay..
The Question:
Solid calcium carbonate is commonly used in antiacids because it reacts with the hydrochloric acid found in the stomach. The products of this reaction are aqueous calcium chloride, carbon dioxide, and water.

My answer:
CaCO3 (s) + HCl (l)= CaCl (aq) + CO2 (g)+ H2O (l)

I think it's right . However, I typed it in a site to check for the balancing and it said the reaction is impossible. Why? And Is it right?

Dear,This reaction is very much possible without any doubt.
but you have written the formula for calcuim chloride wrong.may be u have miss spelt it.I am writing it corrrectly here.

CaCO3 + HCl=CaCl2 + CO2 + H2O

Ohh ! Thanks a loot! =]
It's a shame I didn't pay attention to that! :$

No problems man,just keep in mind
U can't always correct your mistakes.
All d best.

Okay..
The Question:
Solid calcium carbonate is commonly used in antiacids because it reacts with the hydrochloric acid found in the stomach. The products of this reaction are aqueous calcium chloride, carbon dioxide, and water.

My answer:
CaCO3 (s) + HCl (l)= CaCl (aq) + CO2 (g)+ H2O (l)

I think it's right . However, I typed it in a site to check for the balancing and it said the reaction is impossible. Why? and Is it right?

sodium bicarbonate = sodium carbonate + carbon dioxide + water