Final answer:
The correct starting chemical equation for the combustion of methane is CH4 + 2O2 → CO2 + 2H2O. This balanced equation ensures accurate stoichiometric calculations required for determining the percent yield. An error in balancing or in math calculations can lead to an incorrect yield.
Step-by-step explanation:
When starting with the chemical equation for the combustion of methane, the correct starting equation is CH4 + 2O2 → CO2 + 2H2O. This equation is balanced, as it satisfies the requirement that the number of atoms for each element should be the same on both the reactants and products side. In this equation, we have one carbon atom on both sides, four hydrogen atoms on both sides, and four oxygen atoms on both sides when we count the oxygens in both carbon dioxide and water molecules.
It is important to begin with the correct formulae and to balance the equation correctly to calculate the percent yield. An error in the chemical equation could lead you to calculate an erroneous percent yield. However, even with the correct equation, if you made a math error, you could still end up with the incorrect percent yield. Remember, the coefficients in front of the chemical formulas indicate the relative numbers of moles of each substance involved, which should always be represented using the smallest possible whole-number ratios for clarity and convention.