An element X has a tribromide with the empirical formula XBr3 and a trichloride with the empirical formula XCl3. The tribromide is converted to the trichloride according to the equation
XBr3 + Cl2→ XCl3 + Br2
If the complete conversion of 1.334 g of XBr3 results in the formation of 0.722 g of XCl3, what is the atomic mass of the element X?