Answer:
percentage composition = 13.2%
Step-by-step explanation:
percentage of magnesium in magnesium bromide can be found by molar mass of magnesium over molar mass of magnesium bromide.
Molar mass of elements can be found using a standard IUPAC Periodic Table.
M(Mg) = 24.31 g/mol
M(MgBr₂) = 24.31 + 79.90×2 = 184.11 g/mol
∴ percentage composition = 13.2%