Ответ:
1) BaCO3+2HCl=BaCl2+CO2+H2O
+ - 2+ -
BaCO3+2H+2Cl=Ba+2Cl+CO2+H2O
+ 2+
BaCO3+2H=Ba+CO2+H2O
2)Mg(NO3)2+2NaOH=2NaNO3+Mg(OH)2
2+. - +. - +. -
Mg+2NO3+2Na+2OH=2Na+2NO3+Mg(OH)2
2+. -
Mg+2OH=Mg(OH)2
3)Zn(NO3)2+K2S=2KNO3+ZnS
2+. - + 2- +. -
Zn+2NO3+2K+S=2K+2NO3+ZnS
2+. 2-
Zn+S=ZnS
4)3FeCl2+2Al=2AlCl3+3Fe