Suppose a chemist has two fatty acids and wants to identify which one is saturated and which one is unsaturated. She has discovered that they have the same chain length. She can identify the saturated fatty acid because it has more

With the same chain length, a saturated fatty acid has no carbon–carbon double bonds, so it holds the maximum number of hydrogen atoms. An unsaturated fatty acid has one or more double bonds and therefore fewer hydrogens. The saturated fatty acid has more hydrogen atoms, choice C.

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