How can I find the percent compositions of CuBr2?

So, you would first start by finding the molar mass of CuBr2.

Mass of Cu: 63.546

Mass of Br: 79.904

So you take the molar mass:

1(63.546) + 2(79.904) = 223.354

(Remember there's a 2 in front of the of Br due to its subscript.)

After taking the molar mass, you can start solving for percent compositions.

To find percent compositions, it's

(Part / Whole) X 100

So for the of Cu:

(Mass of Cu/ Molar Mass) X 100

(63.546/223.354) X 100 = 28

So it would be 28% for Cu's percent composition

Percent composition of Br:

Remember, Br is a diatomic so there's a subscript of 2.

{2(79.904) / 223.354} X 100 = 71.5

So it would be 71.5% for Br2's percent composition.

Hope this helps!