Question

Calculate Percent Yield:

Palm oil was used for the creation of soap. The mass of the oil was 2.001 grams. The base used was 3 M of NaOH. After the experiment, the mass of the soap was 1.622 grams. What is the percent yield?

The average molar mass of the palm oil is 847.3 grams per mol. The average molar mass of the soap is 291.7 grams per mol. 3 mL of the base (NaOH) was used.

Answer 1

Ans. Number of moles of palm oil = mass / molecular mass

                                                = 2.001 g / 847.3 g mol^-1 = 0.0023616 moles

Number of moles of NaOH = Molarity of NaOH x volume of NaOH solution in L

                                    = 3 moles L^-1 x 0.003 L = 0.009 moles                [1 M = 1 mol L^-1]

Number of moles of Soap = mass / molecular mass

                                    = 1.622 g / 291.7 g mol^-1

                                    = 0.0055605 moles

Compare the number of moles of NaOH, palm oil and soap_. Since, palm oil has only one carboxylic acid group, each mole can react with 1 mole of NaOH only. NaOH is apparently the reagent in excess.

The number of moles of soap > number of moles of palm oil.

In absence of more data, like stoichiometry of the saponification reaction in agreement with relative number of moles of the reactant and the product, % purity (if any), the only way to calculate % yield is direct assessment.

            % yield = (mass of palm oil taken / mass of soap yield) x 100

                        = (2.001 g / 1.622 g) x 100 = 123.36 %

That is more amount of soap is produced than the amount of palm oil taken.