[Cpatel]

Hello. In my general chemistry lab we had to determine the empirical formula of Copper Sulfide through an experiment.
The lab was done by putting a piece of copper in a crucible + adding sulfur. We boiled the crucible till a chemical reaction took place and everything was black (inside).

These were the results:
mass of copper: .4241g
mass of sulfur:   1.145mg

thus
moles of sulfur: 35.71μ
moles of copper: 6.674m

from this the empirical formula is C187 S1.

That doesn't seem correct. Is it? If not what have I done wrong?

All advise/help is appreciated. Thank You.

[Borek]

What was the exact procedure - what have you done - step by step, what and when was weighed?

[Cpatel]

What was the exact procedure - what have you done - step by step, what and when was weighed?

1) Weigh crucible = 21.5953g
2) Add copper wire to crucible
3) Weigh crucible + copper wire = 22.0194g
4) Add sulfur (approx .5 - 1.5g) to crucible. This was done by eye, no real measurements needed according to manual.
5) Heat crucible up till everything is black
6) Weigh crucible =  22.1339g
7) Add more sulfur
8.) Heat crucible up till everything is black
9) Weigh crucible = 22.1347g

And from this we need to determine the empirical formula.

[Borek]

And how you calculated mass of sulfur?