JAMB Chemistry 2010 Paper

Concept:The oxide of nitrogen formed when copper reacts with trioxonitrate(V) acid depends on the concentration of the acid used.Explanation:With 50% trioxonitrate(V) acid, the acid behaves as a dilute acid.Dilute $\mathrm{HNO}_3$ reacts with copper turnings and is reduced to nitrogen(II) oxide.The balanced equation for the reaction is:$$3\mathrm{Cu} + 8\mathrm{HNO}_3 \rightarrow 3\mathrm{Cu(NO_3)_2} + 2\mathrm{NO} + 4\mathrm{H_2O}$$Hence, the gas produced and collected is nitrogen(II) oxide.If concentrated $\mathrm{HNO}_3$ were used, $\mathrm{NO}_2$ would be formed instead.Answer:A. NO