Răspuns:
-calculez moli si masa de carbonat de magneziu care trebuie sa se gaseasca in solutia molara
c,m= niu/V si ro=m/V
ro=1,176g/ml= 1176g/l
niu=c,mxV= c,mx m/ro= 3,5mol/l x600g/1176g/l=1,786 molMgCO3
m= niuxM= 1,786X(24+12+48) , g=150g
-calculez masa de solutie 70% care contine masa de carbonat calculata
c=mdx100/ms----> ms= mdx100/c= 150x100/70g=214g
-calculez masa de solutie 10% care contine masa de carbonat calculata
ms= 150x100/10g=1500g