$n_{CuO} = \dfrac{10}{80} = 0,125(mol) ;n_{HCl} = 0,3(mol)$
CuO + 2HCl → CuCl2 + H2O
Ban đầu : .....0,125........0,3................................................(mol)
Phản ứng :....0,125........0,25..............................................(mol)
Sau pư : ...........0...........0,05...........0,125...........................(mol)
Vậy :
$C_{M_{HCl\ dư}} = \dfrac{0,05}{0,1} = 0,5M$
$C_{M_{CuCl_2}} = \dfrac{0,125}{0,1} = 1,25M$