Is the formation of the two substances Cu2S and CuS an exception to the law of definite proportions. Explain.?

Answer 1

No. In fact, the existence of two well-defined compounds, CuS and Cu2S underscores the Law of Definite Proportions (Proust). What is at work here is the Law of Multiple Proportions, put forward by John Dalton.

Answer 2

No. the Law of Definite Proportions states that all samples of pure compounds contain the same elements in the same proportion by mass. But here you must remember that Copper comes in two flavors, Copper(I) and Copper (II). Cu+ loses an electron while Cu2+ loses two electrons.l

Answer 3

Remember, they are two DIFFERENT substances, hence what he said above.