The reaction of zinc with nitric acid depends on the concentration of the acid. Zinc is a reactive metal that can reduce nitric acid, but the reduction products vary with concentration.

Step 1: Reaction with Dilute Nitric Acid
With very dilute nitric acid (approximately 1-2%), zinc produces nitrous oxide (N₂O). The balanced chemical equation is: $4\mathrm{Zn}+10\mathrm{HNO}{}_3(\mathrm{dilute})\to 4\mathrm{Zn}(\mathrm{NO}{}_3{}_2)+N_{2}O+5H_{2}O$ However, with moderately dilute nitric acid (approximately 20%), zinc produces nitric oxide (NO). The balanced equation is: $3\mathrm{Zn}+8\mathrm{HNO}{}_3(\mathrm{dilute})\to 3\mathrm{Zn}(\mathrm{NO}{}_3{}_2)+2\mathrm{NO}+4H_{2}O$ Since the question specifies "dilute nitric acid" without exact concentration, and considering the options, the most commonly accepted product for dilute acid is N₂O.

Step 2: Reaction with Concentrated Nitric Acid
With concentrated nitric acid, zinc produces nitrogen dioxide (NO₂). The balanced chemical equation is: $\mathrm{Zn}+4\mathrm{HNO}{}_3(\mathrm{conc})\to \mathrm{Zn}(\mathrm{NO}{}_3{}_2)+2\mathrm{NO}{}_2+2H_{2}O$ Concentrated nitric acid is a stronger oxidizing agent, leading to the formation of NO₂.

Final Answer: Comparing with the given options, the correct pair is N₂O (from dilute) and NO₂ (from concentrated). Therefore, the answer is the first option: NO₂ and N₂O? Wait, let's check the options carefully. The first option says "NO₂ and N₂O", which would imply NO₂ from dilute and N₂O from concentrated, but that is incorrect. The second option is "N₂O and NO₂", meaning N₂O from dilute and NO₂ from concentrated, which is correct. So, the correct choice is the second option: N₂O and NO₂.

Related Topics

Oxidation-Reduction Reactions: These reactions involve transfer of electrons. Nitric acid acts as an oxidizing agent, and zinc acts as a reducing agent. The concentration of HNO₃ determines the extent of reduction and hence the product.

Concentration Effects: In chemistry, the concentration of reactants can significantly influence the products formed, especially in reactions involving oxidizing agents like nitric acid or sulfuric acid.

Important Formulae

The general reduction potential for nitric acid to various nitrogen oxides depends on the medium (acid concentration). The half-reactions are:

For NO₂ formation: $\mathrm{NO}{}_3{}^{-}+2H^{+}+e^{-}\to \mathrm{NO}{}_2+H_{2}O$, E° = 0.79 V

For N₂O formation: $2\mathrm{NO}{}_3{}^{-}+10H^{+}+8e^{-}\to N_{2}O+5H_{2}O$, E° = 1.11 V

Higher concentration of H⁺ (i.e., concentrated acid) favors the reduction to NO₂ due to kinetic and thermodynamic factors.