Based on solute-solvent interactions, arrange the following in order of increasing solubility in n-octane and explain. Cyclohexane, KCl, CH3OH, CH3CN.
The order of increasing solubility in n-octane is: KCl < CH₃OH < CH₃CN < Cyclohexane.
n-octane is a non-polar solvent. According to the principle "like dissolves like," non-polar solutes dissolve readily in non-polar solvents while polar solutes do not.
KCl is an ionic compound and is highly polar, so it has the lowest solubility in non-polar n-octane. CH₃OH (methanol) is a polar molecule capable of hydrogen bonding, hence it has low solubility. CH₃CN (acetonitrile) is polar but less polar than methanol, giving it moderate solubility. Cyclohexane is a non-polar hydrocarbon with similar intermolecular interactions as n-octane, making it the most soluble.
Explanation
This question tests the understanding of the 'like dissolves like' principle mentioned in section 1.3.1 of the textbook. n-octane is non-polar, so solubility depends on how non-polar each solute is. KCl (ionic) is most polar, followed by CH3OH (hydrogen bonding), CH3CN (polar but no H-bonding), and cyclohexane (non-polar hydrocarbon). The answer follows the textbook's guidance that solutes with similar intermolecular interactions to the solvent will be more soluble.
Solution Steps
Step 1: Identify n-octane as a non-polar solvent.
Step 2: Classify each solute by polarity - KCl (ionic/polar), CH3OH (polar with H-bonding), CH3CN (polar), Cyclohexane (non-polar).
Step 3: Apply 'like dissolves like' principle - non-polar solutes are most soluble in non-polar solvents.
Step 4: Arrange in order: least soluble (most polar) to most soluble (least polar).