-se foloseste relatia :
n = m :M----> n=nr. de moli ; m=masa subst. (g ) ;M=masa molara (g/moli )
n=5,6 g : 40 g/moli =0,14 moli Ca
n=980g :98g/moli =10 moli H2SO4
n=3600g :18g/moli=200 moli H2O [ 3,6kg=3600g H2O]
n=156g : 78g/moli=2 moli Al(OH)3
MH2SO4=2+32+4.16=98----->98g/moli
MH2O=2+16=18----->18g/moli
MAl(OH)3 =27 +3.16 +3=78------>78g/moli