Copper + sulfur create copper sulfide.
It's a lengthy process to find the empirical formula:
Sulfur:
[tex]25.13g * \frac{1 mol}{32.065 g} = 0.78 mol[/tex]
Copper:
[tex]49.87 * \frac{1 mol}{63.546 g} = 0.78mol[/tex]
S:Cu => [tex]\frac{0.78}{0.78} :\frac{0.78}{0.78}[/tex] => [tex](1:1) * 1[/tex] => [tex]1:1[/tex]
The empirical formula would just be [tex]CuS[/tex]
