Which of the following fatty acids would you expect to be more soluble in cyclohexane?

• A. Palmitic acid (16 Cs)
• B. Stearic acid (18 Cs)
• C. Lauric acid (12 Cs)
• D. none of the above

Answer: (B)

Verified step by step guidance

1. Understand the solubility principle: Solubility of a substance in a solvent depends on the similarity of their intermolecular forces. Cyclohexane is a non-polar solvent, so non-polar substances are more soluble in it.
2. Identify the nature of fatty acids: Fatty acids have a hydrophobic hydrocarbon chain and a hydrophilic carboxylic acid group. The longer the hydrocarbon chain, the more non-polar the fatty acid becomes.
3. Compare the fatty acids: Lauric acid has 12 carbon atoms, Palmitic acid has 16 carbon atoms, and Stearic acid has 18 carbon atoms. The longer the carbon chain, the more non-polar the fatty acid.
4. Determine solubility in cyclohexane: Since cyclohexane is non-polar, the fatty acid with the longest hydrocarbon chain (Stearic acid) will be more soluble due to its increased non-polar character.
5. Conclude: Stearic acid, with 18 carbon atoms, is expected to be more soluble in cyclohexane compared to Lauric acid and Palmitic acid, due to its longer non-polar hydrocarbon chain.