Solutions MCQ Quiz - Objective Question with Answer for Solutions - Download Free PDF

CONCEPT:

Colloidal Solutions and Phases of Dispersed Particles

• A colloidal solution is a type of mixture where one substance (the dispersed phase) is distributed in small particles throughout another substance (the dispersion medium). The particle size in a colloidal solution ranges from 1 to 1000 nanometers.
• Colloidal solutions can be classified based on the phase of the dispersed particles and the dispersion medium. Some common types include:
  • Solid in liquid: Examples include paint, ink, or blood.
  • Liquid in liquid: Examples include emulsions like milk or mayonnaise.
  • Gas in liquid: An example is foam, where gas bubbles are dispersed in a liquid medium.
  • Solid in gas: Examples include smoke or dust particles in air.

EXPLANATION:

• Milk: Milk is an example of a liquid in liquid colloidal solution (an emulsion), where fat droplets are dispersed in water. It does not fit the description of a gas dispersed in a liquid.
• Foam: Foam is an example of a gas dispersed in a liquid, which is a colloidal system. In foam, gas bubbles are trapped in the liquid phase, making it a perfect example of a gas-liquid colloidal solution.
• Aerosol: An aerosol is a colloidal system where tiny liquid droplets or solid particles are dispersed in a gas, such as fog or hairspray. This is a liquid or solid dispersed in a gas, not the other way around.
• Gel: A gel is a colloidal system where a solid phase is dispersed in a liquid, so it is a solid in liquid colloid, not a gas in liquid colloid.

Therefore, the correct answer is 2) Foam, which is a colloidal solution where gas is dispersed in a liquid.

CONCEPT:

Negative Deviation from Ideal Solution Behavior

• A solution exhibits negative deviation from ideal behavior when the intermolecular interactions between different components (A and B) are stronger than the interactions between the molecules of the same component (A-A or B-B).
• In an ideal solution, the enthalpy of mixing (Δmix H) is zero and the volume of mixing (Δmix V) is also zero. Negative deviation occurs when:
  • The total intermolecular attraction between unlike molecules (A-B) is stronger than that between like molecules (A-A or B-B).
  • This results in a negative enthalpy change (Δmix H
  • The volume of mixing (Δmix V) is typically negative because the molecules pack more efficiently than in the pure components.

EXPLANATION:

• Δmix V = 0 at constant T and P:
  • This statement is incorrect. For a solution exhibiting negative deviation, Δmix V is usually negative, not zero, because the solution becomes more compact due to stronger interactions between unlike molecules.
• Intermolecular attractive forces between A-A and B-B are equal to those between A-B:
  • This statement is also incorrect. In negative deviation from ideal behavior, the intermolecular forces between A-A and B-B are weaker than the intermolecular forces between A-B. This stronger A-B interaction causes the negative deviation.
• Intermolecular attractive forces between A-A and B-B are stronger than those between A-B:
  • This statement is incorrect. In negative deviation, the intermolecular forces between A-A and B-B are weaker than those between A-B, which leads to the negative deviation behavior.
• Δmix H
  • This statement is correct. Negative deviation is associated with a negative enthalpy of mixing (Δmix H

Therefore, the correct statement is Δmix H

CONCEPT:

Freezing Point Depression

• Freezing point depression refers to the lowering of the freezing point of a solvent when a solute is added. This phenomenon is described by the equation:

  ΔTf = i · Kf · m

  where:
  • ΔTf = freezing point depression
  • i = van't Hoff factor (the number of particles the solute dissociates into)
  • Kf = cryoscopic constant (specific to the solvent)
  • m = molality of the solution
• The greater the value of "i" (van't Hoff factor), the greater the freezing point depression. This is because a higher "i" means more particles are present in the solution, which causes a greater reduction in the freezing point.

EXPLANATION:

• 0.01 M NaCl: Sodium chloride dissociates into 2 ions (Na⁺ and Cl⁻), so i = 2.
• 0.01 M K₂SO₄: Potassium sulfate dissociates into 3 ions (2 K⁺ and SO₄²⁻), so i = 3.
• 0.01 M KCl: Potassium chloride dissociates into 2 ions (K⁺ and Cl⁻), so i = 2.
• 0.02 M H₂O: Pure water does not dissociate, so i = 1.
• Since the freezing point depression is directly proportional to the van't Hoff factor, the solution with the highest value of i will exhibit the greatest freezing point depression.
• The highest value of i is 3 for K₂SO₄, meaning it will have the greatest freezing point depression among the given solutions.

Therefore, the correct answer is 0.01 M K₂SO₄, as it will exhibit the highest freezing point depression.

CONCEPT:

Henry's Law and Partial Pressure

• Henry's law states that the partial pressure of a gas in a solution is directly proportional to its mole fraction in that solution. The equation can be expressed as:

  P = KH ⋅ X

  where:
  • P = partial pressure of the gas
  • KH = Henry's law constant
  • X = mole fraction of the gas
• From the above, we can rearrange it to express the mole fraction of water:

  P = KH ⋅ (1 − X_water)

  This indicates that as the mole fraction of water increases, the partial pressure of the gas decreases, resulting in a downward slope in the plot.

EXPLANATION:

• Given the Henry's law constants for the gases W, X, Y, and Z:
  • KH for W = 0.5 kbar
  • KH for X = 2 kbar
  • KH for Y = 35 kbar
  • KH for Z = 40 kbar
• The slope of the plot will be negative because of the inverse relationship between the mole fraction of water and the partial pressure of the gas.
• The y-intercept of the plot will be equal to the Henry's law constant KH for each gas, and it should be in the following order:
  • W (0.5 kbar) has the lowest y-intercept.
  • X (2 kbar) has a higher y-intercept than W.
  • Y (35 kbar) has an even higher y-intercept than X.
  • Z (40 kbar) has the highest y-intercept.
• The correct plot will show the gases in the following order, from lowest to highest y-intercept: W
• The plot will be downward sloping, reflecting the negative relationship between the partial pressure and the mole fraction of water.

Therefore, the correct plot corresponds to option D.

CONCEPT:

Determination of Molar Mass using Osmotic Pressure

• Osmotic pressure (π) is a colligative property and is related to molar mass by the formula:

  π = CRT

  where:
  • π = Osmotic pressure (atm)
  • C = Concentration in mol/L
  • R = Gas constant (0.083 L·atm·K–1·mol–1)
  • T = Temperature in Kelvin
• For solutions of macromolecules like PVC, concentration is expressed in g/L, and:

  C = (W/V) × (1/M) ⇒ π = C × (RT/M)

• If we plot π/C vs C, the slope gives RT/M, so:

  M = RT / slope

EXPLANATION:

⇒ 

⇒ 

If we assume graph between  and C

Assuming π vs C graph

Slope = 

∴  gm/mole

Therefore, the molar mass of PVC is 41,500 g/mol (nearest integer).

The correct answer is Sugar in water.

Key Points

• The physical properties help in separating the homogenous mixtures.
• Those mixtures in which the substances are completely mixed together and are indistinguishable from one another are called homogeneous mixtures.
• A homogeneous mixture is a mixture in which the composition is uniform throughout the mixture.
• Many homogeneous mixtures are commonly referred to as solutions.
• Some of the examples of homogeneous mixtures (or solutions) are Sugar solution, Salt solution, Copper sulphate solution, Seawater, Alcohol and water mixture, Petrol and oil mixture, Soda water etc.

• Heterogeneous mixture:
  • A heterogeneous mixture is a mixture with a non-uniform composition that contains components in different phases.
  • The composition varies from one region to another with at least two phases that remain separate from each other, with clearly identifiable properties.
  • Heterogeneous mixtures contain particles that retain their chemical properties when they are mixed and can be distinguished after they are mixed.
  • The components of heterogeneous mixtures can be separated by the filtration of chemical procedures.
  • The two types of heterogeneous mixtures are suspensions and colloids.
  • Sugar and sand form a heterogeneous mixture. If you look closely, you can identify tiny sugar crystals and particles of sand.
  • Ice cubes in cola form a heterogeneous mixture.

The correct answer is Increase.

Concept:

• Molarity:
  • It is defined as the moles of a solute per litres of a solution.
  • It is also known as the molar concentration of a solution.
• Molality:
  • It is defined as the number of moles of solute per kilogram of solvent.
• Mole fraction:
  • It is the ratio of moles of a component with the total moles of solute and solvent.
• Mass%:
  • It is the percentage of the mass of solute or solvent w.r.t total mass of solution.
• Formulas:

Explanation:

• Molarity depends on the volume of the solution.
• And volume is directly proportional to temperature.
• And when we increase the temperature the volume will increase.
• So the increase in volume leads to a decrease in Molarity as Molarity is inversely proportional to the volume of solution.

​Additional Information

Notes:

• Normality:
  • It is defined as the number of gram equivalent per litre of solution.
  • Also known as equivalent concentration.
  • Normality = Number of gram equivalents / [volume of solution in litres]
• Normality is inversely proportional to temperature.
• ​Volume is directly proportional to temperature.
• Molarity is inversely proportional to volume.
• Molarity is inversely proportional to temperature.
• Molality is not dependent on temperature.

The correct answer is isotonic solutions.

Concept:

• Colligative properties are the properties that depend upon the number of solute particles present in the solution. 
  They are : 
• Lowering of Vapour pressure:
  • The vapour pressure exerted by solute molecules on the surface of the solution decreases as solute particles are added to the solution.
  • The relative lowering vapour pressure as given by Raoult's law is:

​

• Elevation of the boiling point:
• The boiling point of a solution increases as we add solute particles to the pure solvent.
• The elevation in boiling point is directly proportional to the molality of the solution.

​ΔT_b = k_b × m; where m = molality of the solution and kb = molal elevation constant.

• Depression of freezing point:
  • The freezing point of a solution decreases as we add solute particles to the pure solvent.
  • The depression of the freezing point is also proportional to the molality of the solution.

​​ΔTf = k_f × m; where m = molality of the solution and k_f = molal depression constant

• Osmotic pressure:
  • ​When a solution and a pure solvent are separated by a semi-permeable membrane, due to differences in concentration, the solvent particles start moving towards the solution via the membrane. This phenomenon is called osmosis. However, the diffusion can be stopped by applying pressure over the membrane in the solution.
  • The osmotic pressure of a solution is the pressure required to stop osmosis when the solution is separated from pure solvent by a semi-permeable membrane.

​Explanation:

Isotonic solutions:

• Diffusion of solvent molecules takes place when there is a difference of chemical potential (or simply concentration) between two solutions connected by a semi-permeable membrane.
• The diffusion can be stopped by applying a pressure π over the solution. This is the osmotic pressure.
• The osmotic pressure is independent of the nature of the membrane but depends on the following factors:
• The temperature remains constant, the osmotic pressure of a solution is directly proportional to its concentration.

​π = kC ; where C = concentration and k = proportionality constant

• Concentration remaining constant, the osmotic pressure is directly proportional to absolute temperature.

π = kT; where T = temperature

• Combining the two laws, we get

π = CRT; where R = universal gas constant

• The osmosis takes place until and unless the chemical potential of both the solutions becomes the same. This is the state of equilibrium. at this point, both solutions have the same osmotic pressure.
• When two solutions of equimolar concentration having the same osmolarity, are separated by a semi-permeable membrane, no net osmosis will take place, then the solution is called isotonic solutions. This is because the osmotic pressure on both sides is the same.

​Hypotonic solutions:

• When the concentration of solutes in a solution is less as compared to the other solution, it is called a hypotonic solution.
• In a hypotonic solution, diffusion takes place in an inward direction.

​Hypertonic solutions:​

• When the concentration of solutes in a solution is more as compared to the other solution, it is called a hypertonic solution.
• In a hypotonic solution, diffusion takes place in an outward direction.

Hence, two solutions with equal osmotic pressure are called isotonic.

The correct answer is option 1, i.e. Boiling point of water will increase above 373K.

Concept:

Vapour Pressure-

• The pressure at which liquid and vapour can co-exist at a given temperature is called the vapour pressure of the liquid.
• When a liquid is kept in a closed vessel with some free space, it starts to vaporise.
• The vapourisation continues until a state of equilibrium is reached between vapourisation and condensation.
• At equilibrium, the state gets saturated and the pressure exerted by the vapour molecules is called vapour pressure.

Explanation:

Vapour Pressure of Solutions of Solids in Liquids - 

• Liquids vapourise at a given temperature and under equilibrium conditions, the pressure exerted by the vapours of the liquid over the liquid is called vapour pressure.
• If a non-volatile solute is added to a pure liquid, the vapour pressure of the solution at a given temperature is found to be lower than the pure solvent.
• Colligative properties of solutions connected with this decrease of vapour pressure are - 
  • Relative lowering of the vapour pressure of the solvent.
  • Depression of the freezing point of the solvent.
  • Elevation of the boiling point of the solvent, ex: Boiling point of water will increase above 373K. Hence Option 1 is correct.
  • The osmotic pressure of the solution.

Concept:

Mass by mass percentage

Mass by mass percentage of a solute in a solution is the mass of the solute present in 100 grams of the solution.
Formula:

Mass by mass percentage = (Mass of solute / Mass of solution) x 100

Explanation:

• Mass of solute (salt) = 40 g
• Mass of solvent (water) = 320 g

We know,

Mass of solution = Mass of solute + Mass of solvent

= 40 g + 320 g

= 360 g

The equivalent weight of oxalic acid in C₂H₂O₄⋅2H₂O is 63.

• The molecular weight of oxalic acid (C₂H₂0₄) is 90.
• But since Oxalic Acid exists with 2 molecules of water, hence molecular weight of Oxalic acid (C₂H₂O₄⋅2H₂O) = 126
• Now, Equivalent weight = Molecular weight/Basicity
• Therefore, Equivalent Weight = 126/2 = 63 (As 2 is the basicity)
• Basicity here means Oxalic Acid release 2 H⁺ ions

Explanation:-

• Mole fraction is defined as the major concentration of a solute and solvent in terms of the number of moles.
• Mole fraction of a solute(X_A) = n _A  /n _A + n _B 
• Mole fraction of a solute(X_B) = n _B  /n A + n B 

Calculation:- 

⇒ No. of moles = Given mass / Molar mass

⇒ Mole fraction of NaCl = No. of moles in NaCl / Total no. of moles in the solution

⇒ No. of moles of NaCl =  1

⇒ No. of moles of H₂O = Given the mass of H₂O / Molar mass of H₂O 

⇒ No. of moles of H2O = 1000 / 18 = 55.55

Mole fraction of NaCl = No. of moles in NaCl / No. of moles in NaCl + No. of moles of H2O 

⇒ Mole fraction of NaCl =  1 / 1 + 55.5 

⇒ Mole fraction of NaCl = 0.0177 

The Correct Answer is Reverse Osmosis.

Key Points

•  Reverse osmosis is a water purification process that uses a partially permeable membrane to separate ions, unwanted molecules, and larger particles from drinking water. 
•  Applying an external pressure to reverse the natural flow of pure solvent, thus, is reverse osmosis.
• This application is mainly applied in the production of potable water in water plants and in industries. 
• Reverse osmosis works by reversing the principle of osmosis. 
• The salt solution is subjected to pressure and pressed against the semi-permeable membrane.
• Here, the applied pressure is greater than the osmotic pressure.
• Thus, the molecules move from a highly concentrated solution to a less concentrated solution.

Additional Information

• Osmosis: This is the process by which the molecules of a solvent pass through the semi-permeable membrane from a region of lower concentration to a higher concentration.
• It is a natural process.
• Occurs along the potential gradient.
• This is observed during the opening of stomata and absorption of water from the soil by the roots.

Concept:

Molarity (M) is defined as the number of moles of solute (n) divided by the volume (V) of the solution in litres. It is important to note that molarity is defined as moles of solute per litre of solution, not moles of solute per litre of solvent.

Molarity indicates the number of moles of solute present in 1 litre of solution. Formula is:

Calculation:

Given that, 

Amount of NaOH solution = 10 % 

Molar mass of NaOH = 40 g/mol

Thus Number of moles in 1 gram of NaOH, n = 1/40

Whereas molar mass of 10% of NaOH = 10/40=1/4 moles

Volume of 10% of NaOH solution = 100 ml

Thus the Molar mass will be 

Hence, the correct option is (3).

Concept:

• Liquids vapourise at a given temperature and under equilibrium conditions, the pressure exerted by the vapours of the liquid over the liquid is called vapour pressure.
• If a non-volatile solute is added to a pure liquid, the vapour pressure of the solution at a given temperature is found to be lower than the pure solvent.
• Colligative properties of solutions connected with this decrease of vapour pressure are - 
  • Relative lowering of the vapour pressure of the solvent.
  • Depression of the freezing point of the solvent.
  • Elevation of the boiling point of the solvent, ex: Boiling point of water will increase above 373K.

Explanation:

From the above explanation, we can see that depression in freezing point of a solvent is considered as colligative property. 

Whereas freezing point, boiling point and melting point are the point at which substance feezes, boiled and melted at certain specific temperature and pressure