In a mixture of \(\mathrm{A}\) and \(\mathrm{B}\), components show negative deviation when: (a) \(\mathrm{A}-\mathrm{B}\) interaction is stronger than \(\mathrm{A}-\mathrm{A}\) and \(\mathrm{B}-\mathrm{B}\) interaction (b) \(\mathrm{A}-\mathrm{B}\) interaction is weaker than \(\mathrm{A}-\mathrm{A}\) and \(\mathrm{B}-\mathrm{B}\) interaction (c) \(\Delta \mathrm{V}_{\operatorname{mix}}>0, \Delta \mathrm{S}_{\operatorname{mix}}>0\) (d) \(\Delta \mathrm{V}_{\operatorname{mix}}^{\operatorname{mix}}=0, \Delta S_{\operatorname{mix}}^{\operatorname{lix}}>0\)

Vapor pressure is a fundamental concept in the study of solutions and thermodynamics. It is the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases at a given temperature in a closed system. The vapor pressure of a substance is a measure of its tendency to evaporate or sublimate and is directly related to the kinetic energy of its molecules.

Vapor pressure can be understood by imagining a liquid in a sealed container. Some of the molecules at the surface of the liquid will have enough energy to escape into the gas phase. Over time, more molecules enter the gas phase while others return to the liquid. Eventually, an equilibrium state is reached where the number of molecules leaving and returning to the liquid are equal, and the pressure they exert at this stage is the vapor pressure of the liquid.

In an ideal solution, which follows Raoult's Law, the vapor pressure of the solution is directly proportional to the mole fraction of the solvent. However, in a non-ideal solution where there is negative deviation from Raoult's Law, the vapor pressure is lower than expected because the attractive forces between different molecules in the mixture are stronger, leading to a decrease in the number of molecules that have enough energy to escape into the gas phase.

In chemistry, solutions are generally categorized as ideal or non-ideal based on how they comply with Raoult's Law. An ideal solution is one where the components mix completely and the intermolecular forces between unlike molecules are equal to those between like molecules. In the case of an ideal solution, the properties can be predicted by the mole fractions of the components and their individual vapor pressures.

Raoult's Law states that the partial vapor pressure of each component in an ideal solution is equal to the vapor pressure of the pure component multiplied by its mole fraction in the mixture. The total vapor pressure of the solution is the sum of the partial vapor pressures.

On the other hand, non-ideal solutions do not follow Raoult's Law strictly. A negative deviation from Raoult's Law occurs when the interactions between different molecules are stronger than the interactions between similar molecules. Consequently, molecules are less likely to escape into the vapor phase, leading to a lower vapor pressure than predicted. This deviation is important because it impacts the boiling point, freezing point, and vapor pressure of a solution, which are critical for many industrial and research processes.

Intermolecular forces are the forces of attraction or repulsion between molecules. They are crucial for understanding the behavior of molecules in a solution and the deviations from Raoult's Law. There are several types of intermolecular forces, including hydrogen bonds, dipole-dipole forces, London dispersion forces, and ion-dipole forces.

In the context of a negative deviation from Raoult's Law, the central focus is on the comparative strength of the intermolecular forces. When the attractive forces between different components in a mixture (A-B interactions) are stronger than the forces between similar molecules (A-A or B-B interactions), the escape of molecules into the vapor phase is less favored. This stronger attraction keeps more molecules in the liquid state, leading to lower vapor pressure.

This principle is essential when considering mixtures of different substances. The balance of intermolecular forces plays a significant role in the properties of solutions, including their vapor pressure, boiling point, and solubility. In cases where we encounter negative deviations from Raoult's Law, it signals that the solution has unique characteristics that deviate from ideal behavior, primarily due to these intermolecular attractions.