Answer:
18
Step-by-step explanation:
According to conservation of matter (mass), matter can neither be created nor destroyed during a chemical reaction but changes from one form to another. For a chemical to be balanced, it means conservation of matter hold true while unbalanced equation suggests that matter has been created or destroyed. The balanced equation below will give further explanation:
2H2 + O2 —> 2H2O
Reactant:
H => 4 atoms
O => 2 atoms
TOTAL => 4 + 2 = 6
Product:
H => 4 atoms
O => 2 atoms
TOTAL = > 4 + 2 = 6
From the above illustration, we can see that we begin with a total of 6 atoms and also end with a total of 6 atoms.
From the question given above, we were told that the reaction started with 18 atoms. Therefore 18 atoms will also end the reaction.