Question

Table P9 Average Molar Masses MMave for Various Oils and Their Saponification (Fatty Acid Salt) Products Sodium Fatty Acid Salt (Soap) Potassium Fatty Acid Salt (Soap) TAG (g/mol) 847.3 869.4 875.0 876.6 919.8 OIL Palm Coconut Corn Canola Soybean (g/mol) 291.7 299.1 301.0 301.5 315.9 (g/mol) 307.8 315.2 317.1 317.6 332.0

Answer 1

Ans. Balanced reaction of saponification:

            Triacylglyceride (oil) + 3 NaOH ---------> Glycerol + 3 FA-Na⁺

# Given,

            Mass of coconut oil = 1.993 g

            Mass of fatty acid salt (soap) = 0.817 g

Now,

            Moles of coconut oil = Mass / molar mass

                                                =1.993 g / (869.4 / mol)

                                                = 0.0022924 mol

# According to the stoichiometry of balanced reaction, 1 mol coconut oil produces 3 mol soap (fatty-acid salt).

Since the type of salt (whether Na⁺ or K⁺ salt) is not specified, it’s assumed that the resultant soap is Na⁺-salt of fatty acids.

So,

Theoretical moles of soap produced = 3 x moles of coconut oil taken

                                                            = 3 x 0.0022924 mol

                                                            = 0.0068772 mol

Theoretical mass of soap produced = Theoretical moles x Molar mass of Na⁺-salt of FA

                                                            = 0.0068772 mol x (299.1 g/ mol)

                                                            = 2.057 g

# % yield = (Actual mass of soap obtained/ Theoretical mass) x 100

                        = (0.817 g / 2.057 g) x 100

                        = 39.72 %

Note: The % yield may vary slightly depending on the type of fatty acid salt chosen for calculation.