What is the empirical formula for a compound if a sample contains 3.72g of P and 21.28g of Cl?

-PCl5 - PCl3 - P2Cl10 - P2Cl 5

Given 3.72 g of P and 21.28g of Cl, converting these to moles: (3.72 g P) (mol P/30.97 g P) = 0.12 mol P (21.28 g Cl) (mol Cl/35.45 g Cl) = 0.60 mol Cl P:Cl = 0.12/0.60, therefore P: Cl = 1/5 Therefore, PCl5