The optimal molar ratio of salicylic acid to acetic anhydride for synthesizing aspirin with a high yield is 1:1. This is because the balanced chemical equation for the synthesis of aspirin acetylsalicylic acid from salicylic acid and acetic anhydride is:C7H6O3 salicylic acid + C4H6O3 acetic anhydride C9H8O4 aspirin + C2H4O2 acetic acid As seen in the equation, one mole of salicylic acid reacts with one mole of acetic anhydride to produce one mole of aspirin and one mole of acetic acid. Therefore, a 1:1 molar ratio ensures that both reactants are fully consumed, maximizing the yield of aspirin.