Question

and amounts of reactants: 2.01 g salicylic acid + 5.00 mL acetic anhydride (plus 5 drops of 85% phosphoric acid) a) If the density of acetic anhydride is 1.08 g/mL, how much acetic anhydride in grams is used? (0.05 pt.) b) What is the theoretical yield of aspirin? (0.15 pts.) c) What is the limiting reactant? (0.05 pt.) d) What is the purpose of phosphoric acid? (0.05 pt.)

Answer 1

see explanation below

Step-by-step explanation:

Now. According to the context of this problem, I'm assuming you are doing the synthesis reaction of aspirin, which is a 1:1 ratio and the reaction is:

C7H6O3 + C4H6O3 ------> C9H8O4 + CH3COOH

Now that we know the general reaction, first, let's get the mass of acetic anhydride

m = d*V = 1.08 * 5 = 5.4 g

Now, with the molar mass of each reactants:

MM of SA = 138.12 g/mol

MM of AA = 102.09 g/mol

MM of aspyrin = 180.16 g/mol

Let's calculate now the moles:

moles of SA = 2.01 / 138.12 = 0.015 moles

moles of AA = 5.4 / 102.09 = 0.053 moles

As we can see in the reaction, 1 mole of SA reacts with 1 mole of AA but we have 0.015 of SA and 0.053 of AA, This means that the limiting reagent is the SA, therefore, it will be the first to be consumed in the reaction.

Now the theorical yield of Aspirin is:

m = 0.015 * 180.16 = 2.7024 g

The purpose of the phosphoric acid is to convert the anhydride acetic into an acid form, therefore, the Salycid acid (The OH) can act as nucleophile and react with the carbonile of the anydride. In this way, we can form the aspirin,