Q1: Which of the following solutions will follow Raoult's law most closely ?

ANS:A - A solution of benzene, toluene and oxylene.

A solution that will follow Raoult's law most closely is a solution of polar organic compounds (not of homologs of a series). Raoult's law states that the vapor pressure of an ideal solution is directly proportional to the mole fraction of each component in the solution. This law applies to ideal solutions, where the interactions between the molecules of the solvent and solute are similar to those between like molecules (solvent-solvent and solute-solute interactions). In the case of a solution of polar organic compounds (not of homologs of a series), the molecules may have similar polarity and molecular size, leading to similar intermolecular interactions and making the solution behave more ideally. Consequently, such a solution is more likely to closely follow Raoult's law. In contrast, the other options involve solutions with components that may have significantly different molecular sizes, polarities, or interactions, leading to deviations from Raoult's law. For example:

• A solution of benzene, toluene, and xylene involves non-ideal interactions due to differences in molecular size and polarity among the components.
• A 35% solution of camphor in water may involve hydrogen bonding interactions between water molecules and the polar camphor molecules, leading to deviations from Raoult's law.
• A 35% solution of NH3 in water involves ion-dipole interactions between ammonia molecules and water molecules, which also leads to deviations from Raoult's law.