When copper is treated with a certain concentration of nitric acid, nitric oxide and nitrogen dioxide are liberated in  equal volumes according to the equationxCu+yHNO3⟶CuNO32+NO+NO2+H2OThe coefficient x and y are

The balanced equation is Cu→ Cu2++2e−                       ............. (i)H⊕+e−+HNO3⟶NO2+H2O ................. (ii)3H⊕+3e−+HNO3⟶NO+2H2O ................ (iii)  Multiplying Eq. (i) by 2 and adding Eqs. (i), (ii) and (iii), we get2Cu+4H⊕+2HNO3→ 2Cu2++NO2+NO+3H2O or 2Cu+6HNO3⟶2CuNO32+NO2+NO+3H2O ∴ x and y are 2 and 6