Final answer:
The correct coefficient for O2 in the equation C3H3 + O2 -> CO2 + H2O is 5 option (b). This allows for the equation to have a balanced number of oxygen atoms on both sides.
Step-by-step explanation:
In the equation C3H3 + O2 -> CO2 + H2O, the coefficient that belongs in front of the O2 to balance the equation is 5. When balancing chemical equations, it is necessary to have an equal number of each type of atom on both sides of the equation.
Since the oxygen atoms are present in diatomic molecules (O2), all coefficients must result in an even number of oxygen atoms. Considering this, we can adjust and balance the oxygen by making sure there are 10 oxygen atoms on both sides of the equation since CO2 contributes 6 oxygen atoms and H2O contributes 4 oxygen atoms, totaling 10. Therefore, the coefficient of 5 for O2 will provide the 10 oxygen atoms needed on the reactant side.