Solutions

This is a multiple choice answer as classified in NCERT Exemplar

(i) Kkg mol^–1 or K (molality)^-1

(ii) 1.0 M Na₂SO₄

Explanation: When compared to the other three electrolytes, the van't Hoff factor in 1.0 M Na₂SO₄ solution is I > 1 and is the highest. As a result, when compared to the other electrolytes in their 1.0 M solutions, the extent of dissociation in the case of 1.0 M Na₂SO₄ would be the greatest, giving the greatest number of ions.

This is a multiple choice answer as classified in NCERT Exemplar

(ii) The number of solute particles in solution.

This is a multiple choice answer as classified in NCERT Exemplar

(i) Methanol and acetone.

Explanation: The interaction (A-A)* is greater than the interaction (A-B)*. Methanol has greater intermolecular hydrogen bonding than methanol and acetone combined. As a result, methanol and acetone mixes will deviate from Raoult's law in a favourable way. The (A-A)* interaction is the interaction of acetone particles/molecules that do not have any hydrogen bonds between them.

The interaction between the particles / molecules of acetone and methanol is known as the (A-B)* interaction.

This is a multiple choice answer as classified in NCERT Exemplar

(ii) Low atmospheric pressure

Explanation:  The atmospheric pressure drops at high altitude, reducing the solubility of oxygen in blood and tissues.

This is a multiple choice answer as classified in NCERT Exemplar

(iii) Pressure

Explanation:  Because solids and liquids are nearly incompressible, the solubility of a solid in a liquid is unaffected by pressure.

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(ii) Supersaturated

Explanation:  At a certain temperature, a supersaturated solution contains less than the maximum quantity of solute per given amount of solvent. When a small amount of solute is added to a solution like this, it precipitates/crystallizes quickly. A supersaturated solution varies from an unsaturated solution in that it does not precipitate or crystallise when a tiny amount of solute is added to it; instead, it goes into solution and remains dissolved at a specific temperature.

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(iii) Equal to the rate of crystallisation

Explanation : This occurs under equilibrium conditions, i.e. rate of forward reaction (dissolution) = rate of backward reaction (crystallisation).

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(iv) Powdered sugar in hot water.

Explanation: (i) The solubility of a solute/sugar particle increases as its surface area increases. Powdered sugar dissolves more quickly due to its increased surface area.

(ii) Because it provides a cool sensation when touched, sugar dissolving is an endothermic process. Increasing the temperature or using hot water, according to LeChatelier's theory, facilitates sugar breakdown.

This is a multiple choice answer as classified in NCERT Exemplar

(i) Mole fraction

Explanation:  The mole fraction (x) is important for determining the relationship between a solution's concentration and its vapour pressure. Rault's law states that p₁ = x₁ po₁ in a binary solution of two volatile liquids, where p₁ is the vapour pressure of component 1, x1 is its mole fraction in solution, and po₁ is the vapour pressure of pure solvent.