For the reaction 2Mg + O_2 → 2MgO, if 8.0 g of MgO is produced, how many moles of Mg were consumed?

• A. 0.50 mol
• B. 0.10 mol
• C. 0.20 mol
• D. 0.40 mol

Answer: (C)

Verified step by step guidance

1. Identify the balanced chemical equation: \$2\text{Mg} + \text{O}_2 \rightarrow 2\text{MgO}$. This tells us that 2 moles of Mg produce 2 moles of MgO, so the mole ratio of Mg to MgO is 1:1.
2. Calculate the number of moles of MgO produced using its molar mass. The molar mass of MgO is calculated by adding the atomic masses of Mg (approximately 24.3 g/mol) and O (approximately 16.0 g/mol), so \(M_{\text{MgO}} = 24.3 + 16.0 = 40.3\ \text{g/mol}\).
3. Use the formula for moles: \(\text{moles of MgO} = \frac{\text{mass of MgO}}{M_{\text{MgO}}}\). Substitute the given mass of MgO (8.0 g) to find the moles of MgO produced.
4. Since the mole ratio of Mg to MgO is 1:1 from the balanced equation, the moles of Mg consumed are equal to the moles of MgO produced.
5. Conclude that the moles of Mg consumed are the same as the moles of MgO calculated in step 3, which gives the answer to the problem.