Question

(a) Would you expect stearic acid, \(\mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{16} \mathrm{COOH},\) to be more soluble in water or in carbon tetrachloride? (b) Which would you expect to be more soluble in water, cyclohexane or dioxane?

Short answer

(a) Stearic acid would be more soluble in nonpolar carbon tetrachloride (CCl₄) than in polar water due to its long nonpolar hydrocarbon chain dominating the interactions. (b) Dioxane, being a polar compound with hydrogen bonding capacity, is more soluble in water than nonpolar cyclohexane.

Step-by-step solution

(a) Stearic acid solubility in water and carbon tetrachloride

Stearic acid has a polar carboxyl group (\(\mathrm{COOH}\)) and a long nonpolar hydrocarbon chain (\(\mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{16}\)). - Water is a polar solvent, thus it can interact with the polar part of stearic acid. - Carbon tetrachloride is a nonpolar solvent, thus it will interact with the nonpolar hydrocarbon chain of stearic acid. Since the nonpolar hydrocarbon chain in stearic acid is much larger than the polar carboxyl group, the interactions between the nonpolar chain and carbon tetrachloride will dominate. Therefore, stearic acid would be more soluble in carbon tetrachloride (CCl₄) than in water.

(b) Solubility comparison of cyclohexane and dioxane in water

Cyclohexane is a nonpolar compound with no hydrogen bonding capacity, while dioxane has polar bonds and can form hydrogen bonds. - Water is a polar solvent, and it forms hydrogen bonds easily. As a result, dioxane, being a polar compound with hydrogen bonding capacity, is more likely to dissolve in water than the nonpolar compound cyclohexane, which is not capable of forming hydrogen bonds with water molecules. Thus, dioxane is more soluble in water than cyclohexane.