Comprehension
According to the generally accepted definition of the ideal solution there are equal interaction forces acting between molecules belonging to the same or different species. (This is equivalent to the statement that the activity of the components equals the concentration.) Strictly speaking, this concept is valid in ecological systems (isotopic mixtures of an element, hydrocarbons mixtures, etc.). It is still usual to talk about ideal solutions as limiting cases in reality since very dilute solutions behave ideally with respect to the solvent. This law is further supported by the fact that Raoult’s law empirically found for describing the behaviour of the solvent in dilute solutions can be deduced thermodynamically via the assumption of ideal behaviour of the solvent.
Question: 1

Give one example of miscible liquid pair which shows negative deviation from Raoult’s law. What is the reason for such deviation?

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Negative deviation occurs when the intermolecular attraction between dissimilar molecules is stronger than between similar molecules.
Updated On: Jan 14, 2026
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Solution and Explanation

Acetone and chloroform exemplify a miscible liquid pair that exhibits negative deviation from Raoult’s law. This deviation arises because the intermolecular forces between acetone and chloroform molecules are more potent than the forces between identical molecules of acetone or chloroform individually. This enhanced attraction diminishes vapor pressure, thus causing negative deviation from Raoult’s law.
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Question: 2

State Raoult’s law for a solution containing volatile components.

Updated On: Jan 14, 2026
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Solution and Explanation

Raoult’s law dictates that the partial vapor pressure of any volatile component within a solution is in direct proportion to its mole fraction in that solution. This relationship is mathematically represented by the formula:

Raoult's Law Formula:
\( P_A = x_A \cdot P_A^0 \)

In this equation:

  • PA signifies the partial vapor pressure of component A.
  • xA denotes the mole fraction of component A present in the solution.
  • PA0 represents the vapor pressure of pure component A.
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Question: 3

Raoult’s law is a special case of Henry’s law. Comment.

Updated On: Jan 14, 2026
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Solution and Explanation

Henry's law describes the solubility of gases in liquids, stating that the partial pressure of a gas is directly proportional to its mole fraction in the solution. Raoult's law is a specific application of Henry's law applicable to volatile components. Specifically, Raoult's law applies when the solvent is also volatile and both components exhibit similar behavior, thus it is a subset of Henry's law concerning solutions of volatile liquids.
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Question: 4

Write two characteristics of an ideal solution.

Updated On: Jan 14, 2026
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Solution and Explanation

An ideal solution exhibits two key properties:

  1. The enthalpy of mixing (\( \Delta H_{\text{mix}} \)) is nil.
  2. The volume of mixing (\( \Delta V_{\text{mix}} \)) is also nil.
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