Answer:
D) 86.8%
Explanation:
It necessary to use the molar mass of Br (80g/mol) and MgBr2 (184g/mol). The MgBr2 is the 100%, so with a mathematical rule of three we can calculate the percent by mass of bromine.
In the molecule of MgBr2 there are 2 bromine, so the total mass of bromine it is 160g (80gx2):
[tex]\begin{gathered} 184g-100\% \\ 160g-x=\frac{160g*100\%}{184g} \\ x=86.9\% \end{gathered}[/tex]Finally, the percent by mass of bromine is 86.9% (86.8%).
