J.R. S. answered 04/05/20
Ph.D. University Professor with 10+ years Tutoring Experience
2Fe(s) + 3Cl2(g) ===> 2FeCl3(s) ... balanced equation
moles Fe = 18.9 g x 1 mol/55.85 g = 0.338 mol Fe (divided by 2 -> 0.169) = LIMITING REAGENT is Fe
moles Cl2 = 40.3 g x 1 mol/71 g = 0.568 mol Cl2 (divided by 3 -> 0.189)
Maximum mass FeCl3 = 0.338 mol Fe x 2 mol FeCl3/2 mol Fe x 162 g/mol = 54.8 g FeCl3 (3 sig. figs.)
Mass excess reagent remaining:
Started with 0.568 moles Cl2
moles Cl2 used = 0.338 mol Fe x 3 mol Cl2/2 mol Fe = 0.507 moles Cl2 used up
mass Cl2 remaining = (0.568 mol - 0.507 mol) x 71 g/mol = 4.33 g Cl2 remaining
