Balancing C2H6 + O2 first gives 3H2O and 2CO2, which needs seven oxygen atoms. Which O2 coefficient is used before clearing fractions?

1. With 3H2O and 2CO2 as products, the oxygen atoms needed are 3 + 4 = 7. 2. Each O2 molecule supplies 2 O atoms, so the coefficient required is 7 divided by 2. 3. That is 7/2, a fraction, which is allowed as an intermediate step. 4. A coefficient of 5/2 would supply only 5 O atoms and 9/2 would supply 9, so neither matches. 5. The fractions are cleared afterwards by multiplying every coefficient by 2. _Source: OpenStax Chemistry (CC BY 4.0), Ch 4 "Stoichiometry of Chemical Reactions", section 4.1 Writing and Balancing Chemical Equations_