The correct answer is \((4) \, (\text{NO}_2 \text{ and } \text{N}_2\text{O})\). When zinc reacts with concentrated nitric acid, the products are zinc nitrate, nitrogen dioxide, and water. The reaction equation is as follows: \[\text{Zn} + 4\text{HNO}_3(\text{conc.}) \rightarrow \text{Zn(NO}_3\text{)}_2 + 2\text{NO}_2 + 2\text{H}_2\text{O}\] When zinc reacts with dilute nitric acid, the products are zinc nitrate, nitrous oxide, and water. The reaction equation is as follows: \[4\text{Zn} + 10\text{HNO}_3(\text{dil.}) \rightarrow 4\text{Zn(NO}_3\text{)}_2 + 5\text{H}_2\text{O} + \text{N}_2\text{O}\] Therefore, the compounds \(x\) and \(y\) respectively are \(\text{NO}_2\) and \(\text{N}_2\text{O}\).
The other options are incorrect: \(1) \, (\text{NO}_2 \text{ and } \text{NO})\): NO is not a product of the reaction of zinc with concentrated nitric acid. \(2) \, (\text{NO}_2 \text{ and } \text{NO}_2)\): \(\text{NO}_2\) is a product of the reaction of zinc with both concentrated and dilute nitric acid. \(3) \, (\text{N}_2\text{O} \text{ and } \text{NO}_2)\): \(\text{N}_2\text{O}\) is a product of the reaction of zinc with dilute nitric acid, but NO is not a product of the reaction of zinc with concentrated nitric acid. |