$Cu$ `\overset((1))(->)` $CuCl_2$ `\overset((2))(->)` $Cu(OH)_2$ `\overset((3))(->)` $CuO$ `\overset((4))(->)` $Na_2SO_4$ 

`(1)` $2Cu$ `+` $Cl_2$ `\overset(t^@)(->)` $CuCl_2$

`(2)`  $CuCl_2$ `+` $2NaOH$ `to`  $Cu(OH)_2$ `+` $2NaCl$

`(3)` $Cu(OH)_2$  `\overset(t^@)(->)` $CuO$ `+` $H_2O$ 

`(4)` $CuO$ `+` $2NaHSO_4$  `\overset(t^@)(->)` $CuSO_4$ `+` $Na_2SO_4$ `+` $H_2O$ 

`\color{#1AD5F7}{⋆⟡}\color{#1AD5F7}{C}\color{#4DA6E6}{h}\color{#668EDD}{i}\color{#8077D5}{p}\color{#995FCD}{p}\color{#EA2F90}{⟡⋆}`