\(CuO+2HCl \to CuCl_2+H_2O\\ Al_2O_3+6HCl \to 2AlCl_3+3H_2O\\ n_{CuO}=a(mol)\\ n_{Al_2O_3}=b(mol)\\ n_{HCl}=2a+6b=0,08(1)\\ m_{muối}=135a+267b=4,02(2)\\ (1)(2)\\ a=b=0,01(mol)\\ m_{dd}=4,02+0,01.(80+102)=5,84g\\ C\%_{CuO}=\frac{0,01.80}{5,84}.100\%=13,7\%\\ C\%_{Al_2O_3}=\frac{0,01.102}{5,84}.100\%=17,4\%\)