What is the percent by mass of magnesium in MgO?

• A. 75.0%
• B. 40.0%
• C. 28.7%
• D. 60.3%

Answer: (D)

Verified step by step guidance

1. Identify the chemical formula of the compound, which is MgO, meaning it contains one atom of magnesium (Mg) and one atom of oxygen (O).
2. Find the atomic masses of magnesium and oxygen from the periodic table: magnesium (Mg) has an atomic mass of approximately 24.3 g/mol, and oxygen (O) has an atomic mass of approximately 16.0 g/mol.
3. Calculate the molar mass of MgO by adding the atomic masses of magnesium and oxygen: \(\text{Molar mass of MgO} = 24.3 + 16.0\) g/mol.
4. Determine the percent by mass of magnesium in MgO using the formula: \(\text{Percent by mass of Mg} = \left( \frac{\text{Atomic mass of Mg}}{\text{Molar mass of MgO}} \right) \times 100\%\).
5. Substitute the values into the formula and simplify to find the percent by mass of magnesium in MgO.