\(Al2O3+6HCl--.2AlCl3+3H2O\)(1)
\(RO+2HCl-->RCl2+H2O\)(2)
\(n_{Al2O3}=\frac{5,1}{102}=0,05\left(mol\right)\)
\(n_{HCl}=6n_{Al2O3}=0,3\left(mol\right)\)
mà \(n_{HCl}=0,2.2,5=0,5\left(mol\right)\)
=>\(n_{HCl\left(2\right)}=0,5-0,3=0,2\left(mol\right)\)
\(n_{RO}=\frac{1}{2}n_{HCl}=0,1\left(mol\right)\)
\(M_{RO}=\frac{4}{0,2}=40\left(\frac{g}{mol}\right)\)
=>\(R=24\left(Mg\right)\)
=>CTHH:MgO
nAl2O3= 5,1/102= 0,05(mol)
nHCl= 0,2.2,5=0,5(mol)
PTHH: Al2O3 + 6 HCl -> 2 AlCl3 + 3 H2O (1)
0,05___________0,3(mol)
=> nHCl(2)= 0,5-0,3=0,2(mol)
(2) RO + 2 HCl -> RCl2 + H2O
0,1______0,2(mol)
=>M(RO)= 4/0,1= 40(g/mol)
Mà: M(RO)= 16+M(R)
=> 16+M(R)= 40
=> M(R)= 24(g/mol)
=> R là magie (Mg=24)
=> CTHH RO: MgO (Magie Oxit)
