1
Дано
m(Mg)=80 g
Al2O3
----------------
m(AL)-?
80g Xg
AL2O3+3Mg-->3MgO+2Al M(Mg)=24 g/mol , M(Al)=27 g/mol
3*24 2*27
80/72 = X/54
X=80*54/72
X=60 g
ответ 60 г
2)
дано
m(H2SO4)=20 g
NaOH
-------------------
m(Na2SO4)-?
20g Xg
H2SO4+2NaOH-->Na2SO4+2H2O
98 142
M(H2SO4)=98 g/mol , M(Na2SO4)=142 g/mol
20/98 = Х/142
Х=20*142/98
Х=29 г
ответ 16.33 г