60 free MCQs on Solutions with worked answers and explanations. Learn how substances dissolve and form mixtures. Covers concentration terms, colligative properties (boiling point elevation, freezing point depression, osmotic pressure), and ideal vs non-ideal solution behaviour.
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Adding a non-volatile solute lowers the solvent's vapour pressure at every temperature, which is the root cause behind all four colligative properties: it shifts the freezing point down and the boiling point up.
Q1.
A solution is:
Answer: B. A homogeneous mixture of solute and solvent
Why: A solution is a uniform, homogeneous mixture of a solute dissolved in a solvent.
Q2.
The component present in larger quantity in a solution is called:
Answer: B. Solvent
Why: The solvent is the component present in the larger quantity that dissolves the solute.
Q3.
Molarity is defined as:
Answer: B. Moles of solute per litre of solution
Why: Molarity (M) = moles of solute / volume of solution in litres. Unit: mol/L.
Q4.
Molality is defined as:
Answer: B. Moles of solute per kg of solvent
Why: Molality (m) = moles of solute / mass of solvent in kg. It does not change with temperature.
Q5.
When a non-volatile solute is dissolved in a solvent, the vapour pressure:
Answer: B. Decreases
Why: Adding solute reduces solvent molecules at the surface (Raoult's law), lowering vapour pressure.
Q6.
Osmosis is the flow of solvent from:
Answer: B. Lower concentration to higher
Why: Solvent flows from dilute (lower solute concentration) to concentrated solution through a semi-permeable membrane.
Q7.
The boiling point of a solution compared to pure solvent is:
Answer: B. Higher
Why: Boiling point elevation is a colligative property; dissolved solutes raise the boiling point.
Q8.
Henry's law states that solubility of a gas in a liquid is:
Answer: B. Directly proportional to pressure
Why: Henry's law: C = KH × P. More pressure means more gas dissolves.
Q9.
Which of these is a colligative property?
Answer: C. Osmotic pressure
Why: Colligative properties (osmotic pressure, boiling point elevation, etc.) depend on number of solute particles, not their nature.
Q10.
The mole fraction of solute is:
Answer: B. Moles of solute / (moles of solute + moles of solvent)
Why: Mole fraction = n(solute) / (n(solute) + n(solvent)). It is dimensionless and sums to 1 for all components.
Q11.
A homogeneous mixture of two or more pure substances is called a:
Answer: B. solution
Why: A solution is a homogeneous mixture with uniform composition throughout.
Q12.
In a solution, the component present in the larger amount is termed the:
Answer: B. solvent
Why: The solvent is present in excess and dissolves the solute.
Q13.
A solution holding the maximum solute it can dissolve at a given temperature is described as:
Answer: B. saturated
Why: A saturated solution is in equilibrium with undissolved solute at that temperature.
Q14.
Molarity is defined as the number of moles of solute per litre of:
Answer: B. solution
Why: Molarity (M) = moles of solute ÷ volume of solution in litres.
Q15.
Molality is the number of moles of solute per kilogram of:
Answer: B. solvent
Why: Molality (m) = moles of solute ÷ mass of solvent in kilograms.
Q16.
Which concentration term does not change with temperature?
Answer: B. molality
Why: Molality is based on mass, which is temperature-independent, unlike volume-based molarity.
Q17.
The solubility of most solid solutes in water generally ___ as temperature rises:
Answer: B. increases
Why: For most solids, dissolution is endothermic, so solubility increases with temperature.
Q18.
Common table salt dissolved in water is an example of a solution of a:
Answer: A. solid in a liquid
Why: Salt (solid) dissolved in water (liquid) is a solid-in-liquid solution.
Q19.
The solubility of a gas in a liquid generally ___ as temperature rises:
Answer: B. decreases
Why: Dissolving a gas is exothermic, so warming the liquid drives the gas out and lowers its solubility.
Q20.
Colligative properties depend on the number of solute particles and not on their:
Answer: B. nature
Why: Colligative properties depend only on how many particles are present, not on what kind they are.
Q21.
The van 't Hoff factor (i) for completely dissociated CaCl₂ is:
Answer: C. 3
Why: CaCl₂ → Ca²⁺ + 2Cl⁻ gives 3 ions per formula unit, so i = 3.
Q22.
Boiling point elevation for 1 mol NaCl in 1 kg water (Kb = 0.52 K kg/mol) is:
Answer: B. 1.04 K
Why: ΔTb = i × Kb × m = 2 × 0.52 × 1 = 1.04 K. NaCl dissociates into 2 ions (i = 2).
Q23.
Osmotic pressure of 0.1 M glucose at 27°C is:
Answer: B. 2.46 atm
Why: π = CRT = 0.1 × 0.0821 × 300 = 2.46 atm. Glucose is a non-electrolyte (i = 1).
Q24.
According to Raoult's law, vapour pressure of a solution compared to pure solvent:
Answer: B. Is less
Why: P = xsolvent × P°. Adding solute lowers the mole fraction of solvent, reducing vapour pressure.
Q25.
The freezing point depression constant Kf depends on:
Answer: B. Nature of solvent only
Why: Kf is a property of the solvent only. For water Kf = 1.86 K kg/mol; benzene Kf = 5.12 K kg/mol.
Q26.
An ideal solution obeys Raoult's law at:
Answer: C. All concentrations
Why: An ideal solution obeys Raoult's law throughout the entire composition range.
Q27.
Molarity of a 5% (w/v) glucose solution (mol. mass = 180 g/mol) is:
Answer: A. 0.278 M
Why: 5% w/v = 50 g/L. Molarity = 50/180 = 0.278 M.
Q28.
Reverse osmosis applies pressure that is:
Answer: C. Greater than osmotic pressure
Why: Pressure greater than osmotic pressure forces solvent from concentrated to dilute side, purifying water.
Q29.
Two liquids that show a negative deviation from Raoult's law form a solution with which property compared to the ideal case?
Answer: B. Lower vapour pressure than expected from Raoult's law, due to stronger attractive forces between unlike molecules
Why: Negative deviation occurs when solute-solvent attractive forces are stronger than the corresponding forces in the pure components, lowering the escaping tendency of molecules and hence the vapour pressure.
Q30.
Why is the observed value of the van 't Hoff factor (i) less than 1 for a solute like acetic acid in benzene?
Answer: A. Acetic acid molecules associate (dimerise) in benzene, reducing the effective number of particles in solution
Why: In a non-polar solvent like benzene, acetic acid molecules associate through hydrogen bonding to form dimers, decreasing the number of effective particles and giving i less than 1.
Q31.
Henry’s law states that the solubility of a gas in a liquid is directly proportional to its:
Answer: B. partial pressure
Why: Henry’s law: p = K_H·x, so gas solubility rises with its partial pressure above the liquid.
Q32.
Raoult’s law states that the partial vapour pressure of a component equals its pure vapour pressure times its:
Answer: B. mole fraction
Why: For an ideal solution, p_A = p°_A·x_A, where x_A is the mole fraction of A.
Q33.
The relative lowering of vapour pressure of a dilute solution equals the mole fraction of the:
Answer: B. solute
Why: (p° − p)/p° = x_solute, a direct statement of Raoult’s law for a non-volatile solute.
Q34.
Which of these is the fourth colligative property, alongside vapour-pressure lowering, boiling-point elevation and freezing-point depression?
Answer: B. osmotic pressure
Why: Osmotic pressure is the fourth colligative property.
Q35.
Compared with the pure solvent, the boiling point of a solution containing a non-volatile solute is:
Answer: B. higher
Why: Dissolving a non-volatile solute lowers the vapour pressure, so a higher temperature is needed to boil the solution.
Q36.
Compared with the pure solvent, the freezing point of a solution is:
Answer: B. lower
Why: A solute depresses the freezing point, so the solution freezes below the pure solvent’s freezing point.
Q37.
The external pressure that just stops osmosis across a semipermeable membrane is called the:
Answer: B. osmotic pressure
Why: Osmotic pressure is the pressure that exactly halts the net flow of solvent through the membrane.
Q38.
In the equation ΔTb = Kb·m, the constant Kb is called the:
Answer: B. ebullioscopic constant
Why: Kb is the ebullioscopic (molal boiling-point-elevation) constant of the solvent.
Q39.
In the equation ΔTf = Kf·m, the constant Kf is called the:
Answer: B. cryoscopic constant
Why: Kf is the cryoscopic (molal freezing-point-depression) constant of the solvent.
Q40.
Two solutions that have the same osmotic pressure are described as:
Answer: B. isotonic
Why: Isotonic solutions exert equal osmotic pressures, so there is no net solvent flow between them.
Q41.
18 g glucose dissolved in 90 g water at 25°C (P° = 23.8 mmHg). Vapour pressure of solution is:
Answer: A. 23.4 mmHg
Why: n(glucose)=0.1, n(water)=5. x(water)=5/5.1=0.9804. P = 0.9804×23.8 = 23.33 ≈ 23.4 mmHg.
Q42.
0.2 g of a substance in 10 g benzene (Kf = 5.12) lowers freezing point by 0.512°C. Molecular mass is:
Answer: B. 200 g/mol
Why: M = (1000 × Kf × w)/(ΔTf × W) = (1000 × 5.12 × 0.2)/(0.512 × 10) = 1024/5.12 = 200 g/mol.
Q43.
Osmotic pressure of 0.2 M K₂SO₄ (fully dissociated) at 27°C is:
Answer: A. 14.76 atm
Why: K₂SO₄ gives 3 ions (i = 3). π = iCRT = 3 × 0.2 × 0.0821 × 300 = 14.78 ≈ 14.76 atm.
Q44.
For a non-ideal solution showing positive deviation from Raoult's law, the A-B intermolecular forces are:
Answer: B. Weaker than A-A and B-B
Why: Positive deviation occurs when A-B interactions are weaker than A-A and B-B, so molecules escape more easily, raising vapour pressure.
Q45.
6 g of a compound dissolved in 100 mL shows osmotic pressure 6 atm at 27°C. Molecular mass is:
Answer: B. 246 g/mol
Why: C = π/RT = 6/(0.0821×300) = 0.2435 M. M = w/(C×V) = 6/(0.2435×0.1) = 246.4 ≈ 246 g/mol.
Q46.
Henry's law constant for O₂ is 46820 bar at 25°C. Mole fraction of O₂ at partial pressure 0.2 bar is:
Answer: A. 4.27 × 10⁻⁶
Why: p = KH × x → x = p/KH = 0.2/46820 = 4.27 × 10⁻⁶.
Q47.
Boiling point elevation of 0.1 m K₂SO₄ solution (Kb = 0.52, complete dissociation) is:
Answer: A. 0.156°C
Why: ΔTb = i × Kb × m = 3 × 0.52 × 0.1 = 0.156°C. K₂SO₄ gives i = 3.
Q48.
The van 't Hoff factor for 1 M BaCl₂ with degree of dissociation 0.8 is:
Answer: A. 2.6
Why: BaCl₂ → Ba²⁺ + 2Cl⁻ (n = 3 particles). i = 1 + (n-1)α = 1 + (3-1)×0.8 = 1 + 1.6 = 2.6.
Q49.
A solution containing 8 g of a non-volatile solute in 100 g of water shows a boiling point elevation of 0.052°C (Kb for water = 0.52 K kg/mol). What is the molar mass of the solute?
Answer: D. 800 g/mol
Why: Delta-Tb = Kb x (w x 1000)/(M x W); 0.052 = 0.52 x (8 x 1000)/(M x 100), solving gives M = 800 g/mol.
Q50.
A 1% (w/v) solution of a non-electrolyte solute has an osmotic pressure of 0.6 atm at 27°C. What is the approximate molar mass of the solute (R = 0.0821 L atm/K/mol)?
Answer: D. 410 g/mol
Why: 1% w/v means 10 g/L; using Pi = (w/M)(RT/V), 0.6 = (10/M) x 0.0821 x 300, solving gives M approximately 410.5 g/mol.
Q51.
The van’t Hoff factor (i) for a solute that dissociates in solution is:
Answer: B. greater than 1
Why: Dissociation increases the number of particles, so i > 1 (e.g. i ≈ 2 for NaCl).
Q52.
The van’t Hoff factor for a solute that associates (e.g. dimerises) in solution is:
Answer: B. less than 1
Why: Association reduces the number of independent particles, so i < 1 (e.g. benzoic acid in benzene).
Q53.
For 0.1 m NaCl assuming complete dissociation, the van’t Hoff factor i is about:
Answer: B. 2
Why: NaCl → Na⁺ + Cl⁻ gives two particles per formula unit, so i ≈ 2.
Q54.
The osmotic pressure π of a dilute solution is given by:
Answer: A. π = CRT
Why: π = CRT, where C is the molar concentration, R the gas constant and T the absolute temperature.
Q55.
A solution showing positive deviation from Raoult’s law has a vapour pressure that is ___ than predicted:
Answer: B. higher
Why: Positive deviation means weaker A–B interactions, so more molecules escape and the vapour pressure is higher.
Q56.
A liquid mixture that boils at a constant temperature without any change in composition is called an:
Answer: B. azeotrope
Why: Azeotropes distil unchanged because vapour and liquid have the same composition at the boiling point.
Q57.
The elevation of boiling point produced by a non-volatile solute is classified as a ___ property:
Answer: B. colligative
Why: It depends only on the number of solute particles, making it a colligative property.
Q58.
If a cell is placed in a hypertonic solution, water will move ___ the cell:
Answer: B. out of
Why: A hypertonic surrounding has higher solute concentration, so water leaves the cell by osmosis and it shrinks.
Q59.
A solution showing negative deviation from Raoult’s law has component interactions that are:
Answer: B. stronger than in pure liquids
Why: Stronger A–B attractions hold molecules back, lowering the vapour pressure below the ideal value.
Q60.
Abnormally high or low molar masses obtained from colligative measurements are caused by:
Answer: B. dissociation or association of the solute
Why: When the solute dissociates or associates, the actual particle count differs from that assumed, giving an abnormal molar mass.