Question

A mixture of phenol and aniline shows negative deviation from Raoult's law. This is due to the formation of:

• A. Polar covalent bond
• B. Non-polar covalent bond
• C. Intermolecular Hydrogen bond
• D. Intramolecular Hydrogen bond

Hint:

Negative deviation occurs due to strong intermolecular hydrogen bonding between phenol and aniline.

Answer 1

The Correct Option is C

The given question concerns the behavior of a mixture composed of phenol and aniline, specifically observing its deviation from Raoult's law. Let us explore the reasoning that leads to selecting the correct answer:

Understanding the Concepts:

• Raoult's law states that the partial vapor pressure of each component in an ideal mixture is proportional to its mole fraction. An ideal solution shows neither positive nor negative deviation from Raoult's law.
• Negative deviation occurs when the interactions between the different components are stronger than those between the same components. This results in a lower total vapor pressure than what would be expected from an ideal solution.

Analyzing the Mixture:

• Phenol (\( C_6H_5OH \)) has an –OH group capable of hydrogen bonding.
• Aniline (\( C_6H_5NH_2 \)) contains an –NH₂ group, which is also capable of hydrogen bonding.
• When these two substances are mixed, intermolecular hydrogen bonds form between the –OH group of phenol and the –NH₂ group of aniline. This interaction is stronger than the interactions present in the pure substances individually.

Conclusion:

• Due to the formation of these intermolecular hydrogen bonds, the mixture exhibits a negative deviation from Raoult’s law as the new interactions are more robust than the original interactions within pure phenol or pure aniline.

Based on the above reasoning, the correct answer is Intermolecular Hydrogen bond.