Question

1. Starting with 4.2 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.

2. Given that you have calculated the theoretical yield possible from two or more starting reagents, which compound is the limiting reagent?

Select one:

a. the reagent that gives the lowest theoretical yield

b. there is no limiting reagent

c. the reagent that gives the greatest theoretical yield

d. the reagent that gives the greatest theoretical yield and is not just a catalyst

e. the reagent that gives the lowest theoretical yield and is not just a catalyst

3. What is the % yield of the reaction making 2.4 g of acetyl salicylic acid from 8.8 g of salicylic acid, 9.0 mL of acetic anhydride (density 1.082), and 10 drops 85 % weight phosphoric acid (density 1.685)? Use the molecular weights that you have already calculated. Give two significant figures.

4. What is the % yield of the reaction making 2.4 g of acetyl salicylic acid from 8.8 g of salicylic acid, 9.0 mL of acetic anhydride (density 1.082), and 10 drops 85 % weight phosphoric acid (density 1.685)? Use the molecular weights that you have already calculated. Give two significant figures.

Answer 1

molecular weight of acetyl salicylic acid=molar mass=180.157 g/mol

molecular weight of acetic anhydride=molar mass=102.09g/mol

So ,Assuming acetic anhydride is the limiting reagent, all of it will be used up in the reaction

4.2 mL of acetic anhydride with a density of 1.082

mol of acetic anhydride reacted=mass reacted/molar mass=volume*density/molar mass=4.2 ml*(1.082 g/ml)/ 102.09g/mol=4.544g/102.09g/mol=0.0445 mol

Assuming one to one stoichiometry ,1 mol of acetic anhydride yields 1 mol acetyl salicylic acid

So,0.0455 mol of acetic anhydrde will yield=0.0445 mol acetyl salicylic acid=0.0445 mol*molar mass=0.0445 mol* 180.157 g/mol=8.019 g

Theoretical yield of acetyl salicylic acid=8.019 g