Answer:
Nitrogen
Step-by-step explanation:
The element nitrogen cannot be a product in the given reaction.
The reaction is;
HCl + CaCO₃
According to the law of conservation of matter, "matter is neither created nor destroyed in the cause of a chemical reaction".
The law suggests that, in a chemical reaction, we end up with the same species we started with. Although due to rearrangement of bonds, new compounds can form;
Starting atoms
H
Cl
Ca
O
These species will also be found in the product.