Question:
Molecules of benzoic acid (C$_{6}H_{5}$COOH) dimerise in benzene. $'w' \,g$ of the acid dissolved in $30\, g$ of benzene shows a depression in freezing point equal to $2K$. If the percentage association of the acid to form dimer in the solution is $80$, then $w$ is :
(Given that $K_{f} = 5 K\, kg\, mol^{-1} $, Molar mass of benzoic acid $= 122 \,g\, mol^{-1})$
Molecules of benzoic acid (C$_{6}H_{5}$COOH) dimerise in benzene. $'w' \,g$ of the acid dissolved in $30\, g$ of benzene shows a depression in freezing point equal to $2K$. If the percentage association of the acid to form dimer in the solution is $80$, then $w$ is :
(Given that $K_{f} = 5 K\, kg\, mol^{-1} $, Molar mass of benzoic acid $= 122 \,g\, mol^{-1})$
Updated On: Sep 14, 2024
- 1.8 g
- 2.4 g
- 1.0 g
- 1.5 g
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The Correct Option is B
Solution and Explanation
$ { 2 \underset{Wg}(C_6H_5 COOH) ->[\text{C_6H_6}][\text{(30 g)}] \underset{diner}(C_6H_5 COOH)_2}$
$\Delta_1 T \, \, = \, i \, k_r \, m$
$2 = 0.6 \times \, 5 \, \times \, \, \frac{w \times 1000}{122 \times 30}$
$(i = 1 - 0.8 +0.4 = 0.6)$
$w = 2.44\, g$
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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:
- Unsaturated Solution- A solution in which more solute can be dissolved without raising the temperature of the solution is known as an unsaturated solution.
- 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.
- Supersaturated Solution- A solution that contains more solute than the maximum amount at a certain temperature is known as a supersaturated solution.