Effect of concentration of nitric acid on the formation of oxidation product can be understood by its reaction with conc `HNO_(3)`. Dilute and concentrated nitric acid give different oxidation products on reaction with copper metal.
`3Cu+8HNO_(3)(Dil.) to 3Cu(NO_(3))_(2)+2NO+4H_(2)O`
`Cu+4HNO_(3)(Conc.)toCu(NO_(3))_(2)+2NO_(2)+2H_(2)O`
