What’s the percent composition for cubr2

To find the percent composition of a compound, divide an element's molar mass by the molar mass of the whole compound. Then multiply by 100 since it's a percent. You do the same for other elements in the compound. When finished with the calculations, all the percents added together should equal near 100%


Molar mass of Cu(copper) is 63.546 g/mol

Molar mass of Br(bromine) is 79.904. Since it is Br2, we must multiply the molar mass of bromine by 2, making it 159.808 g/mol

Molar mass of the whole compound is 223.354 g/mol

Percent Composition of Cu =  %

Percent Composition of Br2 = %

So, the answer is 28.45% Cu and 71.55% Br2.

To make sure it's correct, i'll add both percents to see if its near 100%

28.45% + 71.55% = 106% which is near 100%.