In a chemical reaction that conserves atoms, if you start with 6 carbon atoms, how many carbon atoms must be in the products?

• A. 12 atoms of carbon (C)
• B. 3 atoms of carbon (C)
• C. 6 atoms of carbon (C)
• D. 2 atoms of carbon (C)

Answer: (C)

Atoms are conserved in a chemical reaction, so the total number of each type of atom stays the same from reactants to products. If you start with six carbon atoms, those six carbons must appear somewhere in the products as well. They can be spread across different product molecules, but the total count remains six. If you ended with more or fewer carbon atoms, that would imply carbon was created or destroyed, which doesn’t happen in ordinary chemical reactions. So the carbon count in the products must be six.