Question

Saturated fatty acids will contain ______ hydrogens than unsaturated fatty acids. Multiple choice question. fewer the same number of more

Answer 1

If the two fatty acids contain an equal number of carbon atoms, the saturated fatty acid would contain more hydrogen atoms than the unsaturated one.

Step-by-step explanation:

A fatty acid molecule is made up of two parts:

• an aliphatic hydrocarbon chain (possibly very long,) and
• a carboxyl group (
  `-{\rm COOH}`.)

The fatty acid is considered "saturated" if the hydrocarbon chain part contains only single carbon-carbon bonds. If the hydrocarbon chain of that fatty acid contains carbon-carbon double or triple bonds (such as
`-{\rm CH} = {\rm CH} -` and
`- {\rm C} \equiv {\rm C} -`,) that fatty acid would be "unsaturated."

Each carbon atom typically needs four covalent bonds. For every additional carbon-carbon bond in the chain, one carbon-hydrogen bond would need to be deleted from both sides. Thus, adding one carbon-carbon bond would reduce the number of hydrogen atoms in the acid by two. For example:

• 
  `- {\rm CH_(2) } - {\rm CH_(2)} -` (single bonds only) includes four hydrogen atoms.
• An extra carbon-carbon bond would bring the number of hydrogen atoms down by two:
  `-{\rm CH} = {\rm CH} -`.
• Another carbon-carbon bond would again bring that number by two more:
  `- {\rm C} \equiv {\rm C} -`.

Assume that the unsaturated fatty acid includes the same number of carbon atoms as the saturated fatty acid. The unsaturated fatty would include more carbon-carbon bonds, fewer carbon-hydrogen bonds, and therefore fewer hydrogen atoms overall.