Acompunds whose empirical formula is xf3 consists of 65% f by mass. what is the atomic mass of x

Empirical formula of compound is XF3

Compound consist of 65% F

In 100g of compound there is 65 g of F

= 65 / 19 moles of Fluorine = 3.421 moles

So moles of X = 3.421 / 3 = 1.140 moles

And in 100 g  X consist of 35 g

So the molar mass of X = 35 / 1.140 = 30.71 g = 31 approximately

And it is the mass of phosphorus

So the empirical formula for the compound is PX3

kepler used the data from tycho blahe (his mentor) to construct the laws of planetary motion.