How much salicylic acid does aspirin contain?

Aspirin is made by the reaction of salicylic acid with acetic an hydride what is the theoretical yield of aspirin if 85.0 grams of salicylic acid is treated with excess acetic an hydride?

• Answer:

  Since salicylic acid is being reacted with excess acetic anhydride, salicylic acid is the limiting reactant of the reaction. The balanced equation of the reaction of salicylic acid and acetic anhydride indicates that their is a 1:1:1:1 ratio between every reactant and product. Based on this, it can be concluded that the moles of salicylic acid, if reacted entirely, will yield an equivalent amount of moles of aspirin. To find the theoretical yield, you must know the molecular weight of aspirin and salicylic acid. First, the amount of moles of salicylic acid must be calculated by dividing the gram amount of salicylic acid, which is 85 grams, and dividing it by its molecular weight, which is 138.12 grams per mole. 85.0/138.12= 0.615 moles of salicylic acid This is the mole amount of salicylic acid as well as the theoretical mole amount of aspirin. To convert the mole amount of aspirin into grams, this figure be multiplied by the molecular weight of aspirin, which is 180.1598 0.615 x 180.1598 = 111 grams of aspirin (when rounded to 3 significant figures)