Sulfur and fluorine react to form sulfur hexafluoride. S(s) + 3F2(g) → SF6(g) If 50.0 g S is allowed to react as completely as possible with 105.0 g F2(g), what mass of excess reactant is left? a. 20.5 g S b. 45.7 g F2 c. 15.0 g S d. 36.3 g F2