JEE Main Chemistry Question (2026) — Solution

Step-by-step solution

The partial pressure of a component in a binary mixture follows Raoult's law for ideal solutions: P_ i = x_i P°_i, which is linear. However, the acetone-CS₂ system exhibits positive deviation from ideality due to different molecular interactions. When acetone and CS₂ mix, the hydrogen bonding between acetone molecules is disrupted, and the weaker interactions between unlike molecules allow molecules to escape more easily into the vapor phase. This results in partial pressures higher than predicted by Raoult's law, causing the pressure vs mole fraction curve to bow upward above the ideal line. Graph (1) shows this positive deviation curve correctly.