Răspuns:
CaO
raportul atomic = r.a.
r.a.=1Ca : 1O=1 : 1
r . m.=ACa :AO=40 : 16 [se simplifica cu 8 ]
=5:2
Comp. procentuala prin raport de masa
5+2=7
7g CaO----------5g Ca----------2gO
100g CaO----------xg--------------yg
x=100.5 :7=71,43%Ca
y=100.2 :7=28,57% O