Giải:\(\eqalign{1)\;Cr + 2HCl\buildrel {} \overlongrightarrow CrC{l_2} + {H_2} \uparrow \cr & 2)\;CrC{l_2} + 2NaOH\buildrel {{t^0}} \overlongrightarrow Cr{(OH)_2} \downarrow + 2NaCl. \cr 3)\;4Cr{(OH)_2} + {O_2} + 2{H_2}O\buildrel {} \overlongrightarrow 4Cr{(OH)_3}. \cr 4)\;Cr{(OH)_3} + NaOH\buildrel {} \overlongrightarrow Na[Cr{(OH)_4}{\rm{]}} \cr & 5)\;2CrC{l_2} + Cl_2\buildrel {{t^0}} \overlongrightarrow 2CrC{l_3} \cr & 6)\;Cr{(OH)_3} + 3HCl\buildrel {} \overlongrightarrow CrC{l_3} + 3{H_2}O. \cr} \)
