What is the approximate percent composition by mass of cabr2 (formula mass =200)

20% calcium and 80% Bromine

Our compound is CaBr₂

Formula mass = 200 g

Relative atomic mass of Ca = 40.078

Relative atomic mass of Br = 79.904

Therefore;

% composition of Ca = (40.078/200) 100%

                                  = 20.039

                                  = 20 %

% composition of Br = (79.904×2)/200) 100%

                                 = 79.904 %

                                = 80%

Therefore; the approximate % composition by mass of CaBr₂ is 20% calcium and 80% Bromine

i believe the answer is three water molecules