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

20% calcium and 80% Bromine

Explanation: The percentage composition of an element in a compound is given by dividing the mass of the element in the compound by the relative formula mass of the compound and expressing it as a percentage. % Composition = (mass of element in 1 mole of compound / relative formula mass of the compound) 100%

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