The optimal ratio of aniline to nitric acid to obtain the maximum yield of p-nitroaniline during the preparation process is 1:1. This is because the reaction between aniline and nitric acid follows a simple stoichiometry:C6H5NH2 aniline + HNO3 nitric acid C6H5NHO2 p-nitroaniline + H2OIn this reaction, one mole of aniline reacts with one mole of nitric acid to produce one mole of p-nitroaniline and one mole of water. To achieve the maximum yield, it is essential to maintain a 1:1 molar ratio of the reactants. However, it is important to note that this reaction is typically carried out in the presence of a strong acid, such as sulfuric acid, to facilitate the nitration process.