What is the molar mass (formula weight) of magnesium nitrate, Mg(NO3)2?

• A. 148.3 g/mol
• B. 62.0 g/mol
• C. 180.4 g/mol
• D. 85.0 g/mol

Answer: (A)

Verified step by step guidance

1. Identify the chemical formula of magnesium nitrate, which is Mg(NO\_3)\_2. This means the compound contains 1 magnesium (Mg) atom, 2 nitrogen (N) atoms, and 6 oxygen (O) atoms (because each nitrate ion NO\_3 contains 3 oxygen atoms, and there are 2 nitrate ions).
2. Find the atomic masses of each element from the periodic table: magnesium (Mg) ≈ 24.3 g/mol, nitrogen (N) ≈ 14.0 g/mol, and oxygen (O) ≈ 16.0 g/mol.
3. Calculate the total mass contributed by each element by multiplying the atomic mass by the number of atoms in the formula: for Mg, multiply by 1; for N, multiply by 2; for O, multiply by 6.
4. Add all these contributions together to get the molar mass of magnesium nitrate: \(\text{Molar mass} = (1 \times M_{Mg}) + (2 \times M_{N}) + (6 \times M_{O})\).
5. Sum the values to find the total molar mass in grams per mole, which represents the formula weight of magnesium nitrate.