To determine the number of atoms present in the reaction where 10 atoms of carbon (C) react with 20 atoms of oxygen (O) to form 10 molecules of carbon dioxide (CO₂), we need to account for all the atoms on both sides of the reaction.
- Carbon atoms: There are 10 carbon atoms in the reactants.
- Oxygen atoms: There are 20 oxygen atoms in the reactants. Each molecule of CO₂ contains 2 oxygen atoms, so the 10 molecules of CO₂ will contain \(10 \times 2 = 20\) oxygen atoms.
Now we can calculate the total number of atoms in the reactants:
- Total atoms = Carbon atoms + Oxygen atoms = 10 (C) + 20 (O) = 30 atoms.
According to the law of conservation of matter, the total number of atoms must remain the same before and after the reaction. Thus, the total number of atoms present in this reaction is 30.
The correct response is: 30