Question

Starting with 4.6 mL of acetic anhydride with a density of 1.082, how many grams of acetylsalicylic acid (theoretical yield) can be made? Assume acetic anhydride is the limiting reagent and a one to one stoichiometry. Use the molecular weights that you have already calculated. Give two significant digits.

Answer 1

We can make 8.8 grams of acetylsalicylic acid

Step-by-step explanation:

Step 1: Data given

acetic anhydride = C4H6O3

Volume of acetic anhydride = 4.6 mL = 0.0046 L

Density acetic anhydride = 1.082 g/mL

acetylsalicylic acid = C9H8O4

Step 2: The balanced equation

C4H6O3 + C7H6O3 → C9H8O4 + C2H4O2

Step 3: Calculate mass acetic anhydride

Mass = density * volume

MAss acetic anhydride = 1.082 g/mL * 4.6 grams

Mass acetic anhydride = 4.9772 grams

Step 4: Calculate moles acetic anhydride

Moles = mass / molar mass

Moles acetic anhydride = 4.9772 grams / 102.09 g/mol

Moles acetic anhydride = 0.04875 moles

Step 5: Calculate moles acetylsalicylic acid

For 1 mol C4H6O3 we need 1 mol C7H6O3 to produce 1 mol C9H8O4 and 1 mol C2H4O2

For 0.04875 moles C4H6O3 we'll have 0.04875 moles C9H8O4

Step 6: Calculate mass acetylsalicylic acid

Mass acetylsalicylic acid = moles acetylsalicylic acid / molar mass acetylsalicylic acid

Mass acetylsalicylic acid = 0.04875 moles * 180.158 g/mol

Mass acetylsalicylic acid = 8.8 grams

We can make 8.8 grams of acetylsalicylic acid

Answer 2

m = 8.7917 g

Step-by-step explanation:

This reaction to form the Acetylsalicylic acid, is the following:

C4H6O3 + C7H6O3 --------> C9H8O4 + C2H4O2

Now, the problem already stated that the limiting reactant is the acetic anhydride (C4H6O3), and it's a 1:1 mole ratio, so this means that the moles of acetic anhydride reacting will be the moles of acetylsalicylic acid formed. We have the volume of the anhydride and density, let's calculate the mass, and then, the moles:

d = m/V ------> m = d * V

m = 1.082 * 4.6 = 4.9772 g

The molar mass of C4H6O3 reported is 102.09 g/mol so the moles are:

moles = 4.9772 / 102.09 = 0.0488 moles

As the mole ratio is 1:1 these moles are the same moles of the acid so:

moles Ac Acid = 0.0488 moles

The reported molar mass of the acid is 180.158 g/mol, then the mass:

m = 0.0488 * 180.158 = 8.7917 g

m = 8.7917 g

This is the theorical yield for the reaction