The ideal ratio of aniline to nitric acid to produce the maximum yield of p-nitroaniline in the preparation process is 1:1. This is because the balanced chemical equation for the nitration of aniline to form p-nitroaniline is:C6H7N aniline + HNO3 nitric acid C6H6N2O2 p-nitroaniline + H2O water As per the stoichiometry of the reaction, one mole of aniline reacts with one mole of nitric acid to produce one mole of p-nitroaniline. Therefore, the ideal molar ratio of aniline to nitric acid is 1:1 for maximum yield.