Which of the following compounds will be most soluble in pentane (C5H12)? Explain your choice. A) pentanol (CH3CH2CH2CH2CH2OH) B) benzene (C6H6) C) acetic acid (CH3CO2H) D) ethyl methyl ketone (CH3CH2COCH3)
Which of the following compounds will be most soluble in pentane (C5H12)? Explain your choice.
A) pentanol (CH3CH2CH2CH2CH2OH)
B) benzene (C6H6)
C) acetic acid (CH3CO2H)
D) ethyl methyl ketone (CH3CH2COCH3)
The Correct Answer and Explanation is:
The compound most soluble in pentane (C₅H₁₂) is:
B) Benzene (C₆H₆)
Explanation:
Solubility depends on the principle of “like dissolves like”—substances with similar intermolecular forces are more likely to be miscible or soluble in each other.
Pentane (C₅H₁₂) is a nonpolar hydrocarbon with only weak London dispersion forces. Therefore, compounds that are also nonpolar or have minimal polarity will dissolve better in pentane. Let’s analyze each option:
A) Pentanol (CH₃CH₂CH₂CH₂CH₂OH):
Although pentanol has a long nonpolar hydrocarbon chain (similar to pentane), it contains a polar hydroxyl group (–OH), which forms hydrogen bonds with water. This makes pentanol partially polar, so while it has some solubility in pentane due to its nonpolar chain, the –OH group reduces its compatibility with nonpolar solvents like pentane. Solubility is moderate, but not the highest among the options.
B) Benzene (C₆H₆):
Benzene is a nonpolar aromatic hydrocarbon with only London dispersion forces. Its molecular structure and lack of polarity make it highly compatible with other nonpolar solvents like pentane. Therefore, it is very soluble in pentane due to the similarity in intermolecular forces.
C) Acetic acid (CH₃CO₂H):
Acetic acid is highly polar and capable of hydrogen bonding due to its carboxylic acid group. It is much more soluble in polar solvents like water than in nonpolar solvents like pentane. Thus, its solubility in pentane is very low.
D) Ethyl methyl ketone (CH₃CH₂COCH₃):
This compound (also called butanone) contains a polar carbonyl group (C=O), making it moderately polar. Although it may have limited solubility in pentane due to its hydrocarbon chain, its polarity is not well-matched with pentane’s nonpolarity.
Conclusion:
Benzene is the most soluble in pentane because both are nonpolar hydrocarbons, and their intermolecular forces (London dispersion) are similar.
