Question

1) Copper reacts with Nitric acid. A brown gas is formed and the solution turns blue, Balance the
by oxidation number method.
Cu + NO, NO,+ Cu2​

Answer 1

the nitric acid is reduced to nitrogen dioxide, a poisonous brown gas with an irritating odor:

Cu(s) + 4HNO3(aq) ——> Cu(NO3)2(aq) + 2NO2(g) + 2H2O(l)