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(c) ceric sulphate

(d) Ethanol and water

(d) All the above

(a) Phenol and aniline

(ii) Assertion and reason both are correct statements but reason is not correct explanation for assertion.

(a) Statement I & II are correct but II is the correct explanation of I.

(a) Statement I & II are correct and II is the correct explanation of I

Option : (b) 373.104 K

1. Solute-solvent interactions: 

For an ideal solution, the interaction between the solvent molecules (A – A), the solute molecules (B – B) and between the solvent and solute molecules (A – B) are expected to be similar. if these interactions are dissimilar, there will be a deviation from ideal behaviour.

2. Dissolution of solute: 

When a solute present in a solution dissociates to give its constituent ions, the resultant ions interact strongly with the solvent and causes deviation from Raoult’s law. e.g., KCI in water deviates from ideal behaviour due to dissociation as K⁺ and Cl^- ion which form strong ion-dipole interaction with water molecules.

3. Association of solute: 

Association of solute molecules can also cause deviation from ideal behaviour. For example in solution acetic acid exists as a dimer by forming intermolecular hydrogen bonds and hence deviates from Raoult’s law.

4. Temperature: An increase in temperature of the solution increases the average kinetic energy of the molecules present in the solution which cause decrease in the attractive force between them. As result, the solution deviates from Raoult’s law. 

5. Pressure: 

At high pressure, the molecules tends to stay close to each other and therefore there will be an increase in their intermolecular attraction. Thus a solution deviates from Raoult’s law at high pressure. 

6. Concentration:

When the concentration is increased by adding solute, the solvent-solute interaction becomes significant. This causes deviation from Raoult’s law.

(c) For very dilute solutions. the solvent obeys Raoult’s law and the solute obeys LIenrys law.

1. Isotonic solution : 

If the osmotic pressure of the two solutions are equal, they are called isotonic solutions.

2. Hypertonic solution :

A solution having higher osmotic pressure than another solution is called hypertonic solution.

(b) Both (A) and (R) are correct and (R) is the correct explanation of (A).

Option : (d) 1.04 K kg mol^-1

(i) Raoult’s law.

(ii) It states that at a given temperature for a solution of volatile liquids, the partial v.p. of each component in the solution is directly proportional to its mole fraction.

(b) A - 2, B - 4, C - 1, D - 3

(a) Both (A) and (R) are correct and (R) is the correct explanation of (A).

1. The electrolyte NaCI dissociates completely into its constituent ions in their aqueous solution. This causes an increase in the total number olparticles present in the solution.

2. When we dissolve 1 mole of NaCI in water it. dissociates and gives 1 mole of Na⁺ and 1 mole of Cl^- . Hence the solution will have 2 moles of particles.

But when we dissolve 1 mole of urea (non electrolyte) in water it appears as 1 mole only. So the colligative property value would be double in NaCl than in urea.

(a) Assertion and Reason are correct and R is the correct explanation of A.

(b) 1.5 

\(\alpha=\frac{i-1}{n-1}=0.5\)

\(\frac{i-1}{n-1}=0.5\)

i – 1 = 0.5 

i = 0.5 + 1 = 1.5

1. In the case of gaseous solute in liquid solvent, the solubility decreases with increase in temperature. 

2. When a gaseous solute dissolves in a liquid solvent, its molecules interact with solvent molecules with weak inter molecular forces when the temperature increases, the average. kinetic energy of the molecules present in the solution also increases. 

3. The increase in kinetic energy breaks (he weak inter molecular forces between the gaseous solute and liquid solvent with results in the release of the dissolved gas molecules to gaseous state.

4. The dissolution of most of the gases in Liquid solvents is an endothermic process, the increase in temperature decreases the dissolution of gaseous molecules.

(c) \(ΔT_b=\frac{K_f\times W_A\times 1000}{M_A\times W_B}\) : Elevation in boiling point

1. Molarity – It is the number of moles of the solute present in one litre of the solution.

2. Colligative properties are those properties which depends only on the number of solute particles.

3. ΔT_b = K_b m

\(=k_b\,\frac{n_B\times1000}{W_A}\)

i.e., ΔT_b α n_B i.e., elevation of boiling point depends on number of moles of solute. Hence, it is a colligative property.

Abnormal colligative property : When the experimentally measured colligative property of a solution is different from that calculated theoretically by the van’t Hoff equation or by the laws of osmosis, then the solution is said to have abnormal colligative property.

Explanation : The colligative property depends on the number of solute particles in the solution but it is independent of their nature. Abnormal values of them arise when the dissolved solute undergoes a molecular change like dissociation or association in the solution.

The observed colligative property (or abnormal colligative property ) may be higher or lower than the theoretical value.

(i) Dissociation of the solute molecules : When a solute like an electrolyte is dissolved in a polar solvent like water, it undergoes dissociation, which results in the increase in the number of particles in the solution.

Hence, 

The observed value of the colligative property becomes higher than the theoretical value, e.g., when one mole of KCl is dissolved in the solution then due to dissociation, KCl → K⁺ + Cl^-, the number of particles increases, hence, the colligative properties like osmotic pressure elevation in the boiling point, etc. increase.

(ii) Association of the solute molecules : When a solute like a non-electrolyte is dissolved in a non-polar solvent like benzene, it undergoes association forming molecules of higher molecular mass. Hence, the number of the particles in the solution decreases. Therefore the colligative properties like osmotic pressure, elevation in the boiling point, etc., are lower than the theoretical value, e.g., n_A → An.

2CH₃COOH → (CH₃COOH)₂

2C₆H₅COOH → (C₆H₅COOH)₂

Number of moles of glucose = 18/180 = 0.1 mol.

Mass of solvent = 1 kg.

Morality of glucose , m = \(\frac{n_8}{W_A}\)

= \(\frac{0.1\,mol}{1\,kg}\)

= 0.1 mol/Kg

Elevation of boiling point ΔT_b = K_b × m

= 0.52 K kg/mol × 0.1 mol/kg = 0.052 K

Since water boils at 373.15 K at 1.013 bar pressure, the boiling point of solution will be

373.15 K + 0.052 K = 373.202 K

1. Colligative properties are those properties of dilute solutions of non-volatile solutes whose value depend upon the number of solute particles irrespective of their nature relative to the total number of particles present in the solution.

2. The four colligative properties

• Relative lowering of vapour pressure 
• Elevation of boiling point 
• Depression of freezing point 
• Osmotic pressure  

(a) Benzene and acetone – Ideal solution

∆T_b = K_b m = K_b x W₂ x \(\frac{1000}{M_2}\) x W₁ 

M₂ = K_b x W₂ x \(\frac{1000}{\Delta T_b}\) x W₁ 

= 7.5 x 0.75 x \(\frac{1000}{0.15}\) x 200 = 187.5 g mol^-1

When maximum amount of solute is dissolved in a solvent at a given temperature, the solution is called Saturated solution.