Răspuns:
Explicație:
n= m : m n=nr. moli ; m=masa subst. ; M=masa molara
M Mg(OH)2 = 24 + 2.16 +2=58-------> 58g/moli
m= n . M
m = 8moli. 58g/moli=464 g Mg(OH)2
58g Mg(OH)2---------2g H
450g ----------------------x
x= 450. 2 : 58=15,51 g H
n= 15,51g : 2g/moli=7,76 moli H2