Which of the following shows positive deviation from Raoult's law ?

Explanation

Solute-solvent interactions: For an ideal solution, the interaction between the solvent molecules (A-A), the soute molecules (B-B) and between the solvent and solute molecules (A-B) are expected to be similar. IF these interactions are dissimilar, there will be diviation from ideal behaviour.
(ii) Dissolution of solute: When a solute present in a solution dissociates to five its constituent ions, the resultant ion interact strongly with the solvent acnd causes deviation from Raoult.s law. e.g., KCl in water deviates from ideal behaviour due to dissciation as `K^(+) and Cl ^(-)` ion which from strong ion-dipole interaction with water molecules.
(iii) Association of slute: Association of solute molecules can also cause deviation from ideal behaviour. For example in solution acetic acid exists as a dimer by forming intermolecular hydrogen bonds and hence deviates from Raoult.s law.
(iv) Temparature: An increase in temperature of the solution increase the average kinetic energy of the molecules present in the solution which cause decrese in the attractive force between them. As result, the solution deviates from Raoult.s law.
(v) Pressure: At high pressure, the molecules tends to stay close to each other and therefore there will be an increase in their intermolecular attraction. Thus a solution deviates from Raoult.s law at high pressure.
Concentration: When the concentration is increased by adding soute, the solvent-solute interaction becomes significant. This causes deviation from Raoult.s law.