\(a,2Al_2O_3\rightarrow\left(đpnc,criolit\right)4Al+3O_2\\ 2Al+6HCl\rightarrow2AlCl_3+3H_2\\ AlCl_3+3NaOH\rightarrow Al\left(OH\right)_3+3NaCl\\ 2Al\left(OH\right)_3\rightarrow\left(t^o\right)Al_2O_3+3H_2O\\ Al_2O_3+3H_2SO_4\rightarrow Al_2\left(SO_4\right)_3+3H_2O\)
\(b,2Cu+O_2\rightarrow\left(t^o\right)2CuO\\ CuO+2HCl\rightarrow CuCl_2+H_2O\\ CuCl_2+2KOH\rightarrow Cu\left(OH\right)_2+2KCl\\ Cu\left(OH\right)_2\rightarrow\left(t^o\right)CuO+H_2O\)