\(Cl_2+H_2->2HCl\)
\(2HCl+Na_2O->2NaCl+H_2O\)
\(Cl_2+H_2\underrightarrow{as}2HCl\)
\(Na_2O+2HCl\rightarrow2NaCl+H_2O\)
\(2NaCl+2H_2O\underrightarrow{đpcmn}2NaOH+H_2+Cl_2\)
\(3NaOH+FeCl_3\rightarrow Fe\left(OH\right)_3\downarrow+3NaCl\)
\(2Fe\left(OH\right)_3\underrightarrow{t^o}Fe_2O_3+3H_2O\)
\(Fe_2O_3+3H_2\underrightarrow{t^o}2Fe+3H_2O\)