Question:

The solution from the following with highest depression in freezing point/lowest freezing point is

Updated On: Jan 4, 2025
  • 180 g of benzoic acid dissolved in benzene
  • 180 g of acetic acid dissolved in benzene
  • 180 g of acetic acid dissolved in water
  • 180 g of glucose dissolved in water
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The Correct Option is C

Solution and Explanation

To determine which solution has the highest depression in freezing point, we need to consider the colligative properties of solutions, specifically the freezing point depression.

Colligative Properties: Freezing point depression is given by the formula:

ΔTf = i · Kf · m

where ΔTf is the depression in freezing point, i is the van 't Hoff factor (number of particles the solute breaks into), Kf is the cryoscopic constant of the solvent, and m is the molality of the solution.

Analyzing Each Option:

  • Option (3): 180 g of acetic acid in water. Acetic acid partially ionizes in water (i ≈ 1). The molality will be relatively high as the solvent is water.
  • Option (2): 180 g of acetic acid in benzene. Acetic acid does not ionize in benzene (i = 1). Benzene has a lower Kf than water, leading to a lesser depression.
  • Option (1): 180 g of benzoic acid in benzene. Similar to option (2), it does not ionize, and its effect will be limited by benzene’s lower Kf.
  • Option (4): 180 g of glucose in water. Glucose does not ionize (i = 1), but its molar mass is higher, leading to a lower molality compared to acetic acid.

Conclusion: Given that acetic acid has a higher molar mass than glucose and ionizes in water, it will result in a greater freezing point depression.

Thus, the solution with the highest depression in freezing point is: 180 g of acetic acid dissolved in water.

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Concepts Used:

Solutions

A solution is a homogeneous mixture of two or more components in which the particle size is smaller than 1 nm.

For example, salt and sugar is a good illustration of a solution. A solution can be categorized into several components.

Types of Solutions:

The solutions can be classified into three types:

  • Solid Solutions - In these solutions, the solvent is in a Solid-state.
  • Liquid Solutions- In these solutions, the solvent is in a Liquid state.
  • Gaseous Solutions - In these solutions, the solvent is in a Gaseous state.

On the basis of the amount of solute dissolved in a solvent, solutions are divided into the following types:

  1. Unsaturated Solution- A solution in which more solute can be dissolved without raising the temperature of the solution is known as an unsaturated solution.
  2. Saturated Solution- A solution in which no solute can be dissolved after reaching a certain amount of temperature is known as an unsaturated saturated solution.
  3. Supersaturated Solution- A solution that contains more solute than the maximum amount at a certain temperature is known as a supersaturated solution.