[kerby99]

I don't know how to determine the empirical formula for a sample of cobalt chloride.
Mass of cobalt chloride examined = 7.24g
Mass of cobalt recovered after analysis = 2.67g

Please, help me out to solve this question.

[Rabn]

One of the very first things that should be done when approaching any problem in chemistry is to convert the masses of a species to moles of that species.  Once you do this the answer should be apparent.