Percent by Mass
Calculate the percent by mass of phosphorus and chlorine in phosphorus trichloride
- Assume one mole of phosporus trichloride. Find the moles of phosphorus and
moles of chlorine.
(1 mol PCl3) (1 mol P/ 1 mol PCl3) = 1 mol P
(1 mol PCl3) (3 mol Cl/ 1 mol PCl3) = 3 mol Cl
- Convert mole of each element to mass of each element.
(1 mol P) (30.97 g P/ 1 mol P) = 30.97 g P
(3 mol Cl) (35.45 g Cl/ 1 mol Cl) = 106.4 g Cl
- Calculate the percent by mass of each element.