Question

which colour is obtained when Cu0 reacts with concentrated HCL?

Answer 1

Heya mate....

Well, it depends on the relative amounts of CuO and HCl. However, when you treat CuO with concentrated HCl. If they are near stoichiometric, then CuCl2 is formed.

CuO + 2HCl → CuCl2 + H2O

and at low concentrations of CuCl2 you will get the hydrated form of Cu(II)

CuCl2 + H2O = Cu(H2O)6 + 2 Cl-

And the solution will be blue. As the concentration of Cl- (or HCl) Cu-Cl complexes will begin to form including :

CuCl2 + Cl- → CuCl3- (Red in solution)
CuCl3- + Cl- → CuCl4(2-) (green to yellow)

So, depending on how much HCl you add relative to CuO, the solution could be blue, red, green, or yellow.

@skb

Answer 2

it will form cucl2 +H2o.........