conditions for non ideal solution
Answers
Explanation:
A non-ideal solution is a solution that does not abide to the rules of an ideal solution where the interactions between the molecules are identical (or very close) to the interactions between molecules of different components. That is, there is no forces acting between the components: no Van-der-Waals nor any Coulomb forces. We assume ideal properties for dilute solutions.
Introduction
We use the concept of non-ideal solutions for concentrated solutions. A variety of forces act on real mixtures, making it difficult to predict the properties of such solutions. Non-ideal solutions are identified by determining the strength and specifics of the intermolecular forces between the different molecules in that particular solution.
Non-ideal solutions can occur two ways:
When intermolecular forces between solute and solvent molecules are less strong than between molecules of similar (of the same type) molecules.
When intermolecular forces between dissimilar molecules are greater than those between similar molecules.
Reminder: A solvent is the major component of a mixture (i.e. water, air) while a solute is the minor component (sugar, carbon dioxide, etc...). A concrete example would be your daily cup of coffee: the coffee itself is the solvent, and anything you add (may it be sugar or cream) will be the solute.
As mentioned above, non-ideal solutions are under study because their properties are not easily predictable, as forces between molecules can fluctuate over time. Non-ideal solutions cannot be defined by Raoult's law or by Henry's law, which are properties specifically unique to ideal mixtures:
Raoult's Law: The vapor pressure of a solvent is proportional to its mole fraction. (for solutions)
Henry's Law: The partial pressure of a gas is proportional to its mole fraction. (for gases)
Since these laws assume that there are no intermolecular interactions, it is evident that they cannot be used for real mixtures, since the mathematical formulas will not hold true anymore due to the fact that the forces will have to be taken into account. However, non-ideal solutions are limited on both sides by these two laws.
There are two main situations that can cause non-ideal solutions to form:
Situation 1: Non-ideal solutions can form when forces of attraction between dissimilar molecules are weaker than between similar molecules. At this point, a heterogeneous (non-mixing) solution may still occur, but it is not always the case.The resulting solution has a larger enthalpy of solution than pure components of the solution, causing the process to be endothermic (heat is absorbed to move the reaction forward).
Answer:
when intermolecular force between solute and solvent molecules are less strong then between molecules of similar molecules.