a) Mg +2HCl --> MgCl2 + H2 (1)
Fe +2HCl --> FeCl2 +H2 (2)
2Al +6HCl --> 2AlCl3 +3H2 (3)
giả sử nMg=x(mol)
nFe=y(mol)
=>mMg=24x(g) =mAl
=>nAl=8/9x(mol)
=>\(\left\{{}\begin{matrix}48x+56y=18,56\\\dfrac{7}{3}x+y=0,73\end{matrix}\right.\)=>\(\left\{{}\begin{matrix}x=0,27\left(mol\right)\\y=0,1\left(mol\right)\end{matrix}\right.\)=>nAl=0,24(mol)
=> mMg=mAl=6,48(g)
mFe=5,6(g)
b) theo (1,2,3)
\(\Sigma\)nHCl=1,38(mol)
=> VHCl=0,69(l)
c) MgCl2 +2NaOH --> Mg(OH)2 +2NaCl (4)
AlCl3 + 3NaOH --> Al(OH)3 +3NaCl (5)
FeCl2 +2NaOH --> Fe(OH)2 + 2NaCl (6)
có thể : NaOH +Al(OH)3 --> NaAlO2 +2H2O (7)
Mg(OH)2 -TO-> MgO +H2O (8)
2Al(OH)3 -to-> Al2O3 +3H2O (9)
4Fe(OH)2 +O2 -to-> 2Fe2O3 +4H2O (10)
nNaOH=1,5(mol)
theo (4,5,6) : \(\Sigma\)nNaOH (PƯ)=1,46(mol)
=> nNaOH=0,04(mol)
theo (7) : nAl(OH)3(7)=nNaOH dư=0,04(mol)
lại có : \(\Sigma\)nAl(OH)3=0,24(mol)
=> nAl(OH)3(9)=0,2(mol)
=>m=29(g)