Answer:
13.2% Mg, 86.8% Br
Explanation:
Mg has a molar mass of 24.31g/mol.
Bromine has a molar mass of 79.90 g/mol.
There is one mole of Mg and two moles of Br in the compound:
79.90x2 + 24.31 = 184.11
So the total molar mass of MgBr2 is 184.11.
A percent tells us a part of a whole, so we will divide each part of the mass into the whole mass.
24.31g Mg / 184.11g MgBr2 = .132
159.8g Br / 184.11g MgBr2 = .868
Multiply these decimals by 100 to make them into a percent.
.132 x 100 = 13.2% Mg
.868 x 100 = 86.8% Br
