nAgCl=\(\dfrac{2,87}{143,5}\)=0,02mol
RCln+nAgNO3→nAgCl+R(NO3)n
⇒nRCln=\(\dfrac{0,02}{n}\)
MRCln=\(\dfrac{1,27n}{0,02}\)=63,5
⇒R=28n
n=2⇒R=56(Fe)
Vậy A3 FeCl2
A1:Fe
A2:HCl
A3:FeCl2
A4:H2
A5:NaOH
A6:Fe(OH)2
A7:NaCl
A8:H2O
A9:O2
A10:Fe(OH)3
A11:Fe2O3
PTHH:
Fe+2HCl→FeCl2+H2
FeCl2+2NaOH→Fe(OH)2+2NaCl
4Fe(OH)2+2H2O+O2→4Fe(OH)3
2Fe(OH)3to→Fe2O3+3H2O
Fe2O3+3H2to→2Fe+3H2O