Formation of a solution from two componets can be considered as :
(i) pure solvent `rarr` separated solvent molecules, `/_\H_(1)`
(ii) Pure solute `rarr`separated molecules,`/_\H_(2)`
(iii) separated solvent and solute molecules`rarr`solution, `/_\H_(3)`
solution so formed will be ideal if :

Options

A. `/_\H_("soln")=/_\H_(1) + /_\H_(2) +/_\H_(3)`
B. `/_\H_("soln")=/_\H_(1) + /_\H_(2) -/_\H_(3)`
C. `/_\H_("soln")=/_\H_(1) -/_\H_(2) -/_\H_(3)`
D. `/_\H_("soln")=/_\H_(3) - /_\H_(1) -/_\H_(2)`

Answer

To determine the conditions under which a solution formed from two components can be considered ideal, we can break down the process into several steps:

### Step 1: Understanding the Components
When forming a solution, we have two components: a pure solvent and a pure solute. The process can be represented as follows:
- (i) Pure solvent → separated solvent molecules (ΔH₁)
- (ii) Pure solute → separated solute molecules (ΔH₂)

### Step 2: Formation of the Solution
Next, we consider the mixing of the separated solvent and solute molecules to form a solution:
- (iii) Separated solvent and solute molecules → solution (ΔH₃)

### Step 3: Enthalpy Changes
In this process, we need to account for the enthalpy changes associated with each step:
- ΔH₁ is the enthalpy change required to separate the solvent molecules.
- ΔH₂ is the enthalpy change required to separate the solute molecules.
- ΔH₃ is the enthalpy change associated with mixing the separated solvent and solute molecules to form the solution.

### Step 4: Condition for Ideal Solutions
For the solution to be considered ideal, the overall change in enthalpy (ΔH) during the formation of the solution should be zero. This means that the energy required to separate the solvent and solute molecules should be equal to the energy released when they are mixed:
- ΔH = ΔH₁ + ΔH₂ + ΔH₃ = 0

This implies that:
- ΔH₃ = ΔH₁ + ΔH₂

### Conclusion
Thus, the solution formed will be ideal if the enthalpy change associated with mixing (ΔH₃) is equal to the sum of the enthalpy changes of the individual components (ΔH₁ and ΔH₂).

### Final Statement
In summary, the formation of an ideal solution requires that the enthalpy change during the mixing of the solute and solvent is zero, indicating that the interactions between the solute and solvent are similar to those in the pure components.

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