[caitcait]

An element X forms an iodide (XI₃) and a chloride (XCl₃). The iodide is quantitatively converted to the chloride when it is heated in a stream of chlorine: 2XI₃+3Cl₂ 2XCl₃+ 3I₂   If 0.6000g  of XI₃   is treated, 0.2832g  of XCl₃ is obtained.  Calculate the atomic weight of the element X and identify the element.

[caitcait]

I dont even know where to start with this, I tried converting everything to moles, but I don't think there is enough information?

[Borek]

There is enough information. Mass change depends on the number of moles of the substance. If there is 1 mole of XI₃, you have three moles of I replaced with Cl - can you calculate mass change for 1 mole? You know mass change of the sample - can you use ratios to calculate number of moles of the substance?