Copper oxide reacts with hydrochloric acid to produce copper chloride and water.
So the basic equation that illustrates this reaction is: CuO + HCl ......> CuCl2 + H2O
Now, we need to balance this equation: the number of copper and oxygen moles are balanced. For each of hydrogen and chlorine, we have one mole as a reactant and two moles as product. Therefore, to balance this, we will add an extra mole of HCl in the reactants.
Based on this, the final balanced equation would be: CuO + 2HCl ................> CuCl2 + H2O