a)
\(3Fe+2O_2\underrightarrow{t^o}Fe_3O_4\)
\(Fe_3O_4+4CO\underrightarrow{t^o}3Fe+4CO_2\)
\(2Fe+6H_2SO_4\rightarrow Fe_2\left(SO_4\right)_3+3SO_2+6H_2O\)
\(Fe_2\left(SO_4\right)_3+3BaCl_2\rightarrow3BaSO_4\downarrow+2FeCl_3\)
\(FeCl_3+3NaOH\rightarrow Fe\left(OH\right)_3\downarrow+3NaCl\)
\(2Fe\left(OH\right)_3\underrightarrow{t^o}Fe_2O_3+3H_2O\)
\(Fe_2O_3+3H_2\underrightarrow{t^o}2Fe+3H_2O\)
\(Fe+2HCl\rightarrow FeCl_2+H_2\)
b)
\(4Al+3O_2\underrightarrow{t^o}2Al_2O_3\)
\(Al_2O_3+6HCl\rightarrow2AlCl_3+3H_2O\)
\(AlCl_3+3NaOH\rightarrow Al\left(OH\right)_3\downarrow+3NaCl\)
\(2Al\left(OH\right)_3+3H_2SO_4\rightarrow Al_2\left(SO_4\right)_3+6H_2O\)
