When __C₂H₆(g) + __O₂(g) → __CO₂(g) + __H₂O(l) is balanced with the smallest whole-number coefficients, what is the coefficient of O₂?

Core Concept

Balance carbons first, placing 4 before CO₂, then balance hydrogens with 6 before H₂O. Counting oxygen atoms on the product side gives 8 from the carbon dioxide plus 6 from the water, for 14 atoms total. Fourteen atoms correspond to 7 O₂ molecules, so the coefficient is 7, matching the full equation 2C₂H₆ + 7O₂ → 4CO₂ + 6H₂O.