Write a balanced equaiton when copper reacts with nitric acid, a brown gas is fromed and the solution turns blue.

Explanation

a. ….(i)
c. Multiply equation (ii) by `2` and add equation (i) and (ii).
`{:(curarrCu^(2+)+cancel(2e^(-))),(4H^(o+)+cancel(2e)+2NO_(3)^(ө)rarr2NO_(2)+2H_(2)O),(ulbar(Cu+4H^(o+)+2NO_(3)^(ө)rarrCu^(2+)+2NO_(2)+2H_(2)O)):}`
It is a balanced redox equation.