mHClO4=1u+35,5u+4*16u=100,5 u
1u---x%
100,5u---100%
x=1%H
35,5u---x%
100,5u---100%
x=35,32%Cl
100%-(1%+35,32%)=%O
%O=63,68%
mMgS=24u+32u=56u
24u---x%
56u---100%
x=42,86%Mg
100%-42,86%=%S
%S=57,14%
mCuSO4=63,5u+32u+4*16u=159,5u
63,5u---x%
159,5u---100%
x=39,81%Cu
32u---x%
159,5u---100%
x=20,06%S
100%-(39,81%+20,06%)=%O
%O=40,13%