Question

Starting with 6.9 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. Give two significant digits.

Answer 1

Ans. Given,

Mass of acetic anhydride = density x volume

                                    = 1.082 g mL^-1 x 6.9 mL = 7.4658 g

1 mol acetic anhydride forms 1 mol Acetylsalicylic acid   ----- statement 1

1 acetic anhydride --------> 1 Acetylsalicylic acid

Number of moles of acetic anhydride = (mass / molecular mass) of acetic anhydride

                                                = 7.4658 g/ 102.09 g mol^-1

                                                = 0.073 mol

So, the number of moles of acetic anhydride = 0.073 mol          

Given, statement 1 and acetic anhydride in the limiting reactant- the number of moles of acetylsalicylic acid produced = 0.073 mol       

Now,

Mass of acetylsalicylic acid produced = (moles x molecular mass) of acetylsalicylic acid

                                                = 0.073 mol x 180.157 g mol^-1

                                                = 13.17480 g = 13.2 g

Therefore, amount of acetylsalicylic acid produced from 7.4658 g acetic anhydride =13.2g