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# Which of the following is true about the reaction of Copper and Nitric Acid?

(1) When Copper is oxidized by concentrated nitric acid, the nitric acid is reduced to nitrogen dioxide

(2) When Copper is oxidized by concentrated nitric acid, the nitric acid is reduced to Nitric oxide (3) When Copper is oxidized by dilute nitric acid, it produces Nitric Oxide (4) When Copper is oxidized by dilute nitric acid, it produces nitrogen dioxide

Answer: (1) and (3) are correct.
Copper is oxidized by concentrated nitric acid, $\text{HNO}_3$, to produce $\text{Cu}^{2+}$ ions; the nitric acid is reduced to nitrogen dioxide, a poisonous brown gas with an irritating odor:
$\quad \text{Cu} + 4\text{HNO}_3 \rightarrow \text{Cu(NO}_3)_2 + 2\text{NO}_2 + 2\text{H}_2{O}$
In dilute nitric acid, the reaction produces nitric oxide instead:
$\quad \text{Cu} + 8\text{HNO}_3 \rightarrow \text{Cu(NO}_3)_2 + 2\text{NO} + 4\text{H}_2{O}$