Match List I with List II

Choose the correct answer from the options given below:

A-II, B-I, C-III

The correct answer is Option (3) → A-II, B-I, C-III.

Let us look at each of the given matches

A. Alcohol + Water: II. Positive deviation

To explain the interaction between alcohol and water, particularly focusing on the concept of deviations from ideal behavior in solutions, let’s break down the situation into two parts:

Alcohol and Water Mixture

When alcohol (like ethanol) is mixed with water, it can exhibit either positive or negative deviations from Raoult's Law, depending on the specific interactions between the molecules involved.

Interactions in the Mixture

Hydrogen Bonding: Both alcohols and water are capable of hydrogen bonding, which means that they can interact strongly with each other.

Molecular Structure: Alcohols contain a hydroxyl (-OH) group that can form hydrogen bonds with water, creating a more organized structure compared to pure substances.

Positive Deviation from Raoult's Law

Positive deviation occurs when the vapor pressure of the solution is greater than what Raoult’s Law would predict. This typically means that the interactions between the different components (alcohol and water) are weaker than the interactions between the molecules of the pure components.

Why Alcohol + Water Shows Positive Deviation:

Weaker Intermolecular Forces: When alcohol and water are mixed, the hydrogen bonds formed between alcohol and water may not be as strong as the hydrogen bonds present in pure alcohol or pure water. This leads to an increase in the vapor pressure of the solution

Increased Vapor Pressure: Because the interactions between the alcohol and water molecules are less favorable compared to the interactions in their pure states, more molecules escape into the vapor phase, resulting in a higher vapor pressure than expected.

Summary

Alcohol + Water exhibits positive deviation because the hydrogen bonding interactions in the mixture are weaker than those in the pure components, leading to an increase in vapor pressure above the predicted values by Raoult's Law.

In conclusion, the interaction of alcohol with water provides a clear example of how deviations from ideal behavior can be understood through the analysis of molecular interactions.

B. Benzene + Toluene : I. Ideal solution

When considering the mixture of benzene and toluene, we can analyze its behavior as an ideal solution based on Raoult's Law and the properties of the two components:

Ideal Solution Characteristics

An ideal solution is one in which the properties of the solution are directly proportional to the concentrations of the components and follows Raoult's Law perfectly. In an ideal solution:

No Change in Volume: When the components are mixed, the total volume of the solution is the sum of the volumes of the individual components.

Similar Intermolecular Forces: The interactions between different components in the mixture are similar in strength to the interactions present in the pure components. This means the forces holding the molecules together in the solution (like van der Waals forces) are comparable to those in the pure substances.

Benzene and Toluene

Molecular Structure

Benzene (C₆H₆): A cyclic hydrocarbon with a planar structure, known for its aromatic stability and relatively low boiling point.

Toluene (C₇H₈): A methyl-substituted derivative of benzene, also aromatic, with a slightly higher boiling point than benzene

Similarities

Chemical Nature: Both benzene and toluene are aromatic hydrocarbons with similar molecular structures and types of intermolecular forces (dispersion forces).

Intermolecular Forces: The interactions between benzene-benzene and toluene-toluene are similar to the interactions between benzene-toluene due to their comparable size, shape, and polarity.

Raoult's Law Application

When mixed, the vapor pressure of the mixture can be predicted by Raoult's Law:

\(P_{solution} = P_{benzene} \cdot X_{benzene} + P_{toluene} \cdot X_{toluene}\)

Where:

\(P_{solution}\) is the vapor pressure of the solution.

\(P_{benzene}\) and \(P_{toluene}\) are the vapor pressures of pure benzene and toluene, respectively.

\(X_{benzene}\) and \(X_{toluene}\) are the mole fractions of benzene and toluene in the mixture.

Conclusion

The benzene + toluene mixture behaves as an ideal solution due to the similar intermolecular forces and the nature of the two components. Their mixture follows Raoult's Law closely, exhibiting no significant deviations in terms of vapor pressure and solution volume. Therefore, this mixture is characterized as an ideal solution.

C. Water + Nitric acid: III. Negative deviation

When considering the solution formed by mixing water and nitric acid (HNO₃), it's important to analyze its behavior in terms of Raoult's Law and the nature of the interactions involved. This mixture exhibits negative deviation from ideal behavior.

Negative Deviation Characteristics

A solution shows negative deviation from ideality when:

The vapor pressure of the solution is lower than expected from Raoult’s Law.

The interactions between the molecules of different components in the solution are stronger than the interactions present in the pure components.

Water and Nitric Acid

Chemical Nature

Water (H₂O): A polar solvent with strong hydrogen bonding among its molecules.

Nitric Acid (HNO₃): A strong acid that ionizes completely in water, also featuring polar characteristics due to its functional groups

Intermolecular Interactions

When water and nitric acid are mixed, they form strong hydrogen bonds between the water molecules and the nitrate ions produced by the dissociation of nitric acid.

The formation of these strong intermolecular interactions leads to a greater stabilization of the liquid phase compared to the gaseous phase, resulting in a lower vapor pressure.

Raoult's Law Application

According to Raoult's Law, the vapor pressure of the solution (\(P_{solution}\)) can be expressed as:

\(P_{solution} = P_{water} \cdot X_{water} + P_{HNO3} \cdot X_{HNO3}\)

However, in the case of mixing water with nitric acid, the observed vapor pressure of the solution is lower than what would be predicted based on the mole fractions and pure component vapor pressures.

Conclusion

The water + nitric acid mixture demonstrates negative deviation due to the enhanced interactions between the molecules (strong hydrogen bonds) compared to those in the pure components. This results in a decrease in vapor pressure, showcasing the solution’s non-ideality.

Summary
In conclusion, when water is mixed with nitric acid, the resulting solution experiences negative deviation from ideal behavior due to stronger interactions formed in the mixture, leading to a lower vapor pressure than predicted by Raoult's Law. This characteristic is important for understanding the properties and behavior of the solution in various chemical and industrial applications.