Two nonpolar organic liquids, hexane (C6H14) and heptane (C7H16), are mixed. Do you expect ΔHsoln to be a large positive number, a large negative number, or close to zero? Fill in the following sentence: ΔHsoln is determined by the relative magnitudes of the "old" solute-solute (ΔHsolute) and solvent-solvent (ΔHsolvent) interactions and the "new" solute-solvent (ΔHmix) interactions. In this process, the energy of mixing hexane and heptane (ΔHmix) is the energy of separating them individually (ΔHsolute + ΔHsolvent), so ΔHsoln is expected to be .

When we mix two non polar organic liquids like hexane and heptane,the resulting mixture formed is an ideal solution.An ideal solution is formed when the force of attraction between the molecules of the two liquids is equal to the force of attraction between the molecules of the same type.

For instance if liquids A and B are mixed,

[tex]F_{A-A}[/tex] = [tex]F_{B-B}[/tex] = [tex]F_{A-B}[/tex]

Hence the condition before and after mixing remains unchanged.

Since enthalpy change is associated with inter molecular force of attraction the enthalpy change for ideal solution is zero.