М(Cu2S) = 63,5*2 + 32 = 159
W(Cu) = Ar(Cu)*n / M(Cu2S) *100% = 63,5 *2 / 159 *100% = 80%
W(S) = Ar(S) *n / М(Cu2S) *100% = 32*1 / 159 *100% = 20%
М(MgO) = 24+16=40
W(Mg) = Ar(Mg) * n / M(MgO) *100% = 24 *1 / 40 *100% = 60%
W(O) = Ar(O)*n / М(MgO) *100% = 16*1 / 40*100% = 40%