Question

When pure methanol is mixed with water, the resulting solution feels warm. Would you expect this solution to be ideal? Explain.

Short answer

The methanol-water solution is not ideal because it feels warm when mixed, indicating that heat is evolved during the mixing process. This exothermic behavior implies that the solute-solvent interactions between methanol and water are stronger than the pure solute-solute and solvent-solvent interactions, resulting in a non-ideal solution.

Step-by-step solution

Understanding Ideal Solutions

An ideal solution is a solution in which the interactions between the solute and solvent particles are essentially the same as those in the pure solvents. In other words, the solute-solvent interactions are equal to the solute-solute and solvent-solvent interactions. This means that there is no change in enthalpy as a result of mixing the solute and solvent, hence, no heat is evolved or absorbed during the process.

Exothermic and Endothermic Solutions

In a non-ideal solution, the solute-solvent interactions are different from the interactions present before mixing. This difference in interactions results in a change in enthalpy. Depending on whether the solute-solvent interactions are stronger or weaker than the solute-solute and solvent-solvent interactions, the solution can be exothermic (heat evolves) or endothermic (heat is absorbed).

Methanol-Water Solution

In the given exercise, when methanol is mixed with water, the resulting solution feels warm, which indicates that heat is evolved during mixing. This means that the solute-solvent interactions, in this case between methanol and water, are stronger than the pure solute-solute and solvent-solvent interactions. Therefore, mixing methanol and water results in an exothermic process.

Conclusion

Based on the observation that the methanol-water solution feels warm, we can conclude that the solution is not ideal, as energy is released in the form of heat due to the difference in solute-solvent interactions compared to the pure solute and solvent. The solution is exothermic and non-ideal.