Which of the following must be true for a solution to be considered ideal?

• A. The temperature of the solution must be below 0 °C.
• B. The solution must be composed of nonpolar molecules only.
• C. The solution must have a solute concentration greater than 1 mol/L.
• D. The intermolecular forces between solute and solvent are equal to those between the pure components.

Answer: (D)

Verified step by step guidance

1. Understand the definition of an ideal solution: An ideal solution is one in which the interactions between different components are similar to the interactions within each pure component.
2. Recall that in an ideal solution, the enthalpy of mixing (ΔH_mix) is zero, meaning there is no heat absorbed or released when the solution forms.
3. Recognize that this condition implies the intermolecular forces between solute and solvent molecules must be equal to those between the molecules of the pure solute and pure solvent.
4. Note that temperature, polarity, or concentration do not strictly define an ideal solution; rather, it is the equality of intermolecular forces that matters.
5. Therefore, the key criterion for an ideal solution is that the intermolecular forces between solute and solvent are equal to those between the pure components.