Final answer:
The equation 2Mg + O₂ → 2MgO is balanced, and with 6 moles of Mg, 3 moles of O₂ are required to react completely according to the stoichiometry of the balanced equation.
Step-by-step explanation:
The chemical equation provided, 2Mg + O₂ → 2MgO, is a balanced equation as it follows the law of conservation of mass. The coefficients indicate the ratio of moles of reactants needed to react completely with each other. To verify if the equation is balanced, we count the atoms of each element on both the reactant and product sides of the equation. There are 2 magnesium atoms on the reactant side and 2 magnesium atoms on the product side. Additionally, there is 1 molecule of oxygen (O₂) on the reactant side, which contains 2 oxygen atoms, and on the product side, there are 2 oxygen atoms within the 2 molecules of magnesium oxide (MgO).
According to the stoichiometry of the balanced equation, 2 moles of Mg react with 1 mole of O₂ to produce 2 moles of MgO. If we have 6 moles of Mg, then 3 moles of O₂ would be needed because the ratio of Mg to O₂ is 2:1. Therefore, with 6 moles of Mg, 3 would be the number of moles of O₂ needed to complete the reaction.