The formula of magnesium chloride is MgCl₂ - OCR Gateway - GCSE Chemistry - Question 4 - 2020 - Paper 1

To find the relative formula mass of magnesium chloride (MgCl₂), we need to sum the atomic masses of its constituents:

1. Identify the elements: Magnesium (Mg) and Chlorine (Cl).
2. Determine the atomic masses:
   • Magnesium (Mg) = 24.3
   • Chlorine (Cl) = 35.5
3. Account for the number of each atom: In MgCl₂, there is 1 magnesium atom and 2 chlorine atoms.
4. Calculation:
   • Mass of Mg: 1 × 24.3 = 24.3
   • Mass of Cl: 2 × 35.5 = 71.0
5. Sum it up: $ext{Relative formula mass} = 24.3 + 71.0 = 95.3$

Thus, the relative formula mass of magnesium chloride is 95.3.