Based on solute-solvent interactions, arrange the following in order of increasing solubility in n-octane and explain. Cyclohexane, KCI, CH3OH, CH3CN.

 The correct arrangement of the given compounds in order of increasing solubility in n-octane is:

KCl < CH3OH< CH3CN < Cyclohexane 

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Explanation based on Solute-Solvent Interactions

The rule governing solubility is "like dissolves like", which means polar/ionic solutes dissolve in polar solvents, and non-polar solutes dissolve in non-polar solvents.

Nature of Solvent: n-Octane (C8H18) is a long-chain hydrocarbon and is entirely non-polar.
Cyclohexane (Most Soluble): Like n-octane, cyclohexane (C6H12) is a non-polar hydrocarbon. The solute-solvent interactions involved are weak London dispersion forces. Because their natures are identical, they mix completely in all proportions.
(CH3CN) (Acetonitrile): It is a polar molecule due to the cyano (-CN) group, but it lacks the capability to form strong intermolecular hydrogen bonds. Therefore, it is less tightly held to itself than methanol and exhibits relatively better compatibility with the non-polar solvent.
(CH3OH) (Methanol): It is a highly polar molecule capable of strong intermolecular hydrogen bonding. Because breaking these hydrogen bonds to fit into a non-polar hydrocarbon solvent is energetically unfavorable, its solubility in n-octane is lower than that of acetonitrile.
KCl (Least Soluble): Potassium chloride is an ionic compound with high lattice energy. Since a non-polar solvent like n-octane cannot provide ion-dipole interactions to break the ionic lattice, KCl is virtually insoluble in it.