Answer:
the empirical formula of the metal fluoride.
Step-by-step explanation:
Mass of copper heated = 8.249 g
Mass of copper fluoride formed = 13.18 g
Mass of fluorine gas in copper fluoride = x

Moles of copper :

Moles of fluorine:

For the empirical formula divide the smallest mole of an element with all the moles of elements present in the compound.

The empirical formula of the copper fluoride =

the empirical formula of the metal fluoride.