Question

Animal fats and vegetable oils are triacylglycerols, or triesters, formed from the reaction

of glycerol (1, 2, 3-propanetriol) with three long-chain fatty acids. One of the methods
used to characterize a fat or an oil is a determination of its saponification number. When
treated with boiling aqueous KOH, an ester is saponified into the parent alcohol and fatty
acids (as carboxylate ions). The saponification number is the number of milligrams of
KOH required to saponify 1.000 g of the fat or oil. In a typical analysis, a 2.085-g sample
of butter is added to 25.00 mL of 0.5131 M KOH. After saponification is complete, the
excess KOH is back titrated with 10.26 mL of 0.5000 M HCl. What is the saponification
number for this sample of butter?

Answer 1

The acidity of every sample based on Mass % of Oleic acid
M(C18H34O2) = 0.2O85g
M(sample) = 10g
= M(C18H34O2)/M(sample) × 100
= 0.2085/10 × 100
= 2.8%
= 18
7