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PUCET (Punjab) Non-Ideal Solutions — practice questions

Explore 121 free Non-Ideal Solutions questions in PUCET (Punjab) Chemistry. Open each question or exercise to read its content, reference answers and available explanation.

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Non-Ideal Solutions questions and exercises with answers

Showing questions 1–30 of 121.

Colligative properties of a dilute solution depend on:Read the answer and worked solution →$36$ g of glucose ($M = 180$ g/mol) is dissolved in $200$ g of water. The molality of the solution is:Read the answer and worked solution →The van't Hoff factor $i$ for a $0.01$ M aqueous solution of NaCl, assuming complete dissociation, is approximately:Read the answer and worked solution →A solution is best defined as:Read the answer and worked solution →In a salt-in-water solution, the solvent is:Read the answer and worked solution →The empirical rule 'like dissolves like' predicts that:Read the answer and worked solution →Which of the following is **not** a colligative property?Read the answer and worked solution →When a non-volatile solute is dissolved in a volatile solvent, the vapour pressure of the solution:Read the answer and worked solution →The boiling point elevation $\Delta T_b$ of a dilute solution is:Read the answer and worked solution →For an **ideal** solution, the enthalpy of mixing $\Delta_{mix}H$ is:Read the answer and worked solution →Raoult's law for a volatile component of a solution states $P_i$ equals:Read the answer and worked solution →With increase in temperature, the solubility of most gases in water:Read the answer and worked solution →If 18 g of glucose (M = 180 g/mol) is dissolved in 90 g of water (M = 18 g/mol), the mole fraction of glucose is approximately:Read the answer and worked solution →Which gas does **not** obey Henry's law in water, because it reacts chemically with the solvent?Read the answer and worked solution →The relative lowering of vapour pressure of a dilute solution of a non-volatile solute equals:Read the answer and worked solution →If $K_b$ for water is 0.512 K·kg/mol, the boiling point elevation of a 0.50 molal aqueous urea solution is:Read the answer and worked solution →A solution that shows **positive** deviation from Raoult's law typically has:Read the answer and worked solution →Solutions are homogeneous mixtures of two or more components. In a binary solution, the component present in the largest quantity is termed the:Read the answer and worked solution →An amalgam of mercury with sodium is an example of which type of solution?Read the answer and worked solution →Which of the following concentration units is *temperature-dependent*?Read the answer and worked solution →The sum of mole fractions of all components in a solution equals:Read the answer and worked solution →Molality (m) is defined as:Read the answer and worked solution →Calculate the molality of a solution prepared by dissolving 2.5 g of ethanoic acid (CH₃COOH, M = 60 g mol⁻¹) in 75 g of benzene.Read the answer and worked solution →The molarity of a solution containing 5 g of NaOH (M = 40 g mol⁻¹) in 450 mL of solution is:Read the answer and worked solution →The mole fraction of ethylene glycol (C₂H₆O₂, M = 62) in a 20% by mass aqueous solution is approximately:Read the answer and worked solution →If sea water (density 1.03 g mL⁻¹) contains 5.8 g of dissolved O₂ per 10⁶ g of water, the concentration is best expressed as:Read the answer and worked solution →'Like dissolves like' implies that:Read the answer and worked solution →If dissolution of a solid in a liquid is endothermic (Δ_sol H > 0), the solubility will:Read the answer and worked solution →Solubility of gases in liquids generally:Read the answer and worked solution →To increase the solubility of CO₂ in soft drinks, manufacturers:Read the answer and worked solution →

Worked practice questions

Colligative properties of a dilute solution depend on:

  1. The pressure only
  2. The temperature only
  3. The number of solute particles, not their nature
  4. The chemical nature of the solute
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Correct answer: C. The number of solute particles, not their nature

By definition, colligative properties (relative lowering of vapour pressure, boiling-point elevation, freezing-point depression, osmotic pressure) depend on how many solute particles are dissolved, not what those particles are. One mole of glucose and one mole of urea cause the same boiling-point elevation in 1 kg of water. With electrolytes like NaCl that dissociate into 2 ions, the effective particle count is multiplied by the van't Hoff factor $i$ (close to 2 for NaCl in dilute solution).

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$36$ g of glucose ($M = 180$ g/mol) is dissolved in $200$ g of water. The molality of the solution is:

  1. $0.5$ mol/kg
  2. $2.0$ mol/kg
  3. $0.1$ mol/kg
  4. $1.0$ mol/kg
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Correct answer: D. $1.0$ mol/kg

Moles of glucose: $\dfrac{36}{180} = 0.2$ mol. Mass of solvent in kilograms: $\dfrac{200}{1000} = 0.2$ kg. Molality: $m = \dfrac{0.2}{0.2} = 1.0$ mol/kg. Note the use of solvent mass (not solution mass) in the denominator: that distinction separates molality from molarity. For very dilute aqueous solutions the two are numerically close, but they diverge for concentrated solutions.

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The van't Hoff factor $i$ for a $0.01$ M aqueous solution of NaCl, assuming complete dissociation, is approximately:

  1. $1$
  2. $0.5$
  3. $2$
  4. $3$
Show answer and solution

Correct answer: C. $2$

NaCl dissociates in water: $\mathrm{NaCl} \rightarrow \mathrm{Na^+} + \mathrm{Cl^-}$. One formula unit produces two particles in solution. Van't Hoff factor $i = \dfrac{\text{actual moles of particles}}{\text{moles of solute formula units}}$. For complete dissociation of NaCl, $i = 2$. In reality, ion pairing slightly reduces $i$ below the theoretical value, especially at higher concentrations. At dilute $0.01$ M the assumption of complete dissociation is reasonable, and the experimental $i$ is close to $1.9$. The question asks for the theoretical value assuming complete dissociation, so 2 is the cleanest answer. Compare with $\mathrm{CaCl_2}$: dissociates into 3 ions, so $i = 3$ (option D) — common trap.

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