2HCl + CuO -> CuCl2 + H2O
73%..
100g soutie...73g HCl
10 g solutie ..7.3gHCl
MHCl = 36.5 => 7.3 g HCl = 0.2 moli
conform reactiei 1 mol CuO reractioneaza cu 2 moli de HCl
x mol CuO... 0.2 moli de HCl
x=0.1 moli de CuO
MCuO = 64 + 16 = 80 g => 0.1 moli de CuO = 0.1*80 = 8 g CuO este necesara