1. MCO=28g/mol
n=m/M=2,8/28=0,1 moli CO
1 mol CO........16g O
0,1 moli CO....x=1,6g O
2. FeCO3
raport atomic => 1:1:3
raport masic => 56:12:48=28:6:24=14:3:24
3. MK2SO4=174g/mol
n=m/M=40/174=
174g K2SO4.....78g K...32g S....64g O
40g K2SO4....x=18g K...y=7g S...z=15g O