IMAT 2021 Q25 [Fatty Acids]

Three fatty acids with the formula C8H16O2 react with glycerol (C3H8O3) to form a triglyceride.

Which of the following is the correct formula for the triglyceride ?

A. C27H50O6
B. C27H48O5
C. C27H48O6
D. C27H52O7
E. C27H56O9

The correct answer is A : C27H50O6

To answer this question, you have proceed in a step by step manner. First, we have to know that glycerol + 3 fatty acids produce a triglyceride and 3 atoms of water (H2O).

Carbon
There are (8 x 3) + 3 = 27 atoms of carbon in this reaction

Hydrogen
There are (3 x 16) + 8 = 56 atoms of hydrogen in this reaction

  • But 3 x 2 = 6 of these atoms of hydrogen form the 3 molecules of H2O released by the reaction
  • So there are 56 - 6 = 50 atoms of hydrogen in the triglyceride

Oxygen
There are (3 x 2) + 3 = 9 atoms of oxygen in this reaction

  • But 3 of these atoms of oxygen form the 3 molecules of H2O released by the reaction
  • So there are 9 - 3 = 6 atoms of oxygen in the triglyceride

Therefore, the formula of the triglyceride is C27H50O6.

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