When aluminum (Al) or lead (Pb) react with dilute nitric acid (HNO3), they do not liberate nitrous gases (such as nitrous oxide, N2O) but instead produce hydrogen gas (H2) and metal nitrates. The reaction proceeds as follows:
Aluminum with dilute nitric acid: 2 Al + 6 HNO3 → 2 Al(NO3)3 + 3 H2
Lead with dilute nitric acid: 3 Pb + 8 HNO3 → 3 Pb(NO3)2 + 2 NO + 4 H2O
As you can see, the reaction of aluminum with dilute nitric acid produces aluminum nitrate (Al(NO3)3) and hydrogen gas (H2). Similarly, the reaction of lead with dilute nitric acid yields lead nitrate (Pb(NO3)2), nitric oxide (NO) gas, and water (H2O).
The formation of nitrous gases, such as nitrous oxide (N2O), would require specific conditions and reactants. However, in the case of the reactions of aluminum and lead with dilute nitric acid, the predominant products are metal nitrates and hydrogen gas.