When a Chemical Equation Is Balanced, It Will Have a Set

Multiple Choice

When a chemical equation is balanced, it will have a set of whole number coefficients that cannot be reduced to smaller whole numbers. What is the coefficient for O₂ when the following combustion reaction of a hydrocarbon is balanced? ___ C₇H₁₄ + ___ O₂ $\rarr$ ___ CO₂ + ___ H₂O

A) 42
B) 21
C) 11
D) 10
E) none of these