To determine the number of carbon (C) atoms in the reactants of the given chemical equation:
\[ C_7H_{16} + O_2 \rightarrow CO_2 + H_2O \]
In the reactants, we have:
- C₇H₁₆: This compound has 7 carbon (C) atoms.
- O₂: This compound contains oxygen atoms, but no carbon atoms.
Thus, in the reactants of the equation, there are a total of 7 carbon atoms.