CuSO₄
Mr(CuSO₄)=160
Ar(Cu)=63,5
Ar(S)=32
w(Cu)=Ar(Cu)/Mr(CuSO₄)
w(Cu)=63,5/160=0,397
w(S)=Ar(S)/Mr(CuSO₄)
w(S)=32/160=0,200
w(O)=1-w(Cu)-w(S)
w(O)=1-0,397-0,200=0,403
H₃PO₄
Mr(H₃PO₄)=98
Ar(H)=1
Ar(P)=31
w(H)=3*Ar(H)/Mr(H₃PO₄)
w(H)=3*1/98=0,031
w(P)=Ar(P)/Mr(H₃PO₄)
w(P)=31/98=0,316
w(O)=1-w(H)-w(P)
w(O)=1-0,031-0,316=0,653
Fe₂(SO₄)₃
Mr{Fe₂(SO₄)₃}=400
Ar(Fe)=56
Ar(S)=32
w(Fe)=2Ar(Fe)/Mr{Fe₂(SO₄)₃}
w(Fe)=2*56/400=0,280
w(S)=3Ar(S)/Mr{Fe₂(SO₄)₃}
w(S)=3*32/400=0,240
w(O)=1-w(Fe)-w(S)
w(O)=1-0,280-0,240=0,480