Question

triglycerides form when three fatty acid molecules combine with one molecule of glycerol, which contains carbon, oxygen, and hydrogen atoms. fatty acids have carbon and hydrogen atoms arranged in long chains. the number of carbon atoms in a fatty acid can range from four to 36!
the models show the chemical structures of stearic acid (a fatty acid) and stearin (a triglyceride).
chemical structure diagrams of stearic acid and stearin
how many molecules of stearic acid are needed to make one molecule of stearin?

Explanation:

Step1: Analyze the structure of stearin

Looking at the stearin structure, we can see the glycerol backbone (the part with the three -OH groups in the formation of triglycerides) and the fatty acid chains attached.

Step2: Recall the formation of triglycerides

Triglycerides are formed when three fatty acid molecules combine with one molecule of glycerol. From the structure of stearin (a triglyceride), we can observe that there are three fatty acid chains (each similar to stearic acid's fatty acid part) attached to the glycerol. Also, the description at the start says "Triglycerides form when three fatty acid molecules combine with one molecule of glycerol". And by visually inspecting the stearin structure, we can count the number of fatty acid - like chains (derived from stearic acid) attached to the glycerol. There are three such chains. So, the number of stearic acid molecules needed is 3.

Answer:

3