1. Na2CO3
MNa2CO3 =2.23 +12 +3.16 =106
Daca in 106kgNa2CO3 se gasesc 48kg O atunci in 212kg Na2CO3 se afla xkg O
106KgNa2CO3-------------48kg O
212kgNa2CO3--------------Xkg O
X=212.48/106=96kg O
AO=16 23
16g O----------------6,023.10 atomi O
96gO-----------------Y
23 23
Y=96.6,023.10 /16 =36,138.10 atomi O
2. Se calculeaza masa subst.dizolvate md din formula concentratiei c
c=md/ms . 100
md=c.ms/100
md=37.572/100=211,64 g Na2CO3
MNa2CO3=106
106 gNa2CO3------------48gO
211,64 gNa2CO3-------X
X=211,64.48/106=95,82 g O