Question

multiple choice question
during the reaction shown below, 5.0 moles of methane gas combine with an unknown amount of oxygen gas. which step should you perform first to determine the number of moles of oxygen molecules involved in this reaction?
ch₄(g) + o₂(g) → co₂(g) + h₂o(g)

convert from grams to moles of the given substance. use the inverse of the molar mass as the conversion factor.

convert from moles of unknown to grams of unknown. use the molar mass as the conversion factor.

convert from moles of the given substance to moles of the unknown substance. use the appropriate mole ratio as the conversion factor.

balance the chemical equation and interpret the equation in terms of moles.

Explanation:

To determine the moles of oxygen in the reaction, the first step is to balance the chemical equation. Balancing gives the correct mole ratios between reactants and products, which is essential for subsequent stoichiometric calculations. The other options assume the equation is already balanced or involve unnecessary conversions (like gram - mole conversions when moles of methane are already given), but without a balanced equation, mole ratios can't be correctly applied.

Answer:

D. Balance the chemical equation and interpret the equation in terms of moles.