CUET UG Chemistry Booster Test 1-Fundamentals of Solutions -

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CUET UG Chemistry Booster Test 1-Fundamentals of Solutions

⏱️ 30 Minutes

❓ 20 Questions

📌 Answers are locked once submitted — results and explanations appear at the end.

CUET UG Chemistry Booster Test 1-Fundamentals of Solutions

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QUESTION 1 OF 20

Match the mixture with its classification based on uniformity:

List 1 (Mixture)	List 2 (Classification based on uniformity)
1. Brass	b. Mixture of copper and zinc
2. German silver	a. Mixture of copper, zinc and nickel
3. Bronze	c. Mixture of copper and tin
4. Sodium chloride in water	d. Homogeneous Liquid Solution

Answer Review

1 Match the mixture with its classification based on uniformity:

List 1 (Mixture)	List 2 (Classification based on uniformity)
1. Brass	b. Mixture of copper and zinc
2. German silver	a. Mixture of copper, zinc and nickel
3. Bronze	c. Mixture of copper and tin
4. Sodium chloride in water	d. Homogeneous Liquid Solution

A 1-b, 2-a, 3-c, 4-d

B 1-c, 2-b, 3-a, 4-d

C 1-a, 2-d, 3-c, 4-b

D 1-b, 2-a, 3-d, 4-c

💡 Short Explanation

Brass is copper and zinc. German silver is copper, zinc and nickel. 1. • Bronze is copper and tin.

✅ Correct Answer Explanation

2. → Brass is an alloy of copper and zinc, German silver contains copper, zinc and nickel, and bronze is an alloy of copper and tin. Sodium chloride dissolved in water forms a homogeneous liquid solution because the salt particles are uniformly distributed in water.

❓ Why Other Options Are Incorrect

Option B → Brass and German silver are incorrectly matched.
Option C → Brass and sodium chloride solution are incorrectly matched.

3. • Option D → Bronze and sodium chloride solution are incorrectly matched.

🎯 Strategy

Used

4. Option Grouping

Application:

Match the known alloy compositions first, then confirm sodium chloride in water as a homogeneous liquid solution.

Final Logic:

Brass = Cu + Zn; German silver = Cu + Zn + Ni; Bronze = Cu + Sn.

🧠 Memory Trick

1. → Brass-Zinc, Bronze-Tin.

📚 2. Class XII – Chemistry Part I – Chapter: Solutions – Topic: Types of Solutions and Alloys

2 Consider a solution prepared by mixing 20 mL of ethanol and 80 mL of water.
A. Ethanol is the solute because it is in lesser quantity.
B. Water is the solvent because it is in larger quantity.
C. Both ethanol and water are considered solutes.
D. The physical state of the solvent determines the physical state of the solution.

A A, B, C

B A, B, D

C B, C, D

D A, D, C

💡 Short Explanation

Ethanol is present in smaller amount. Water is present in larger amount. 1. • Solvent determines the physical state of solution.

✅ Correct Answer Explanation

2. → In a binary liquid solution, the component present in smaller quantity is generally treated as the solute, while the component present in larger quantity is the solvent. Here, ethanol is 20 mL, so it acts as solute. Water is 80 mL, so it acts as solvent. The solvent also determines the physical state of the solution.

❓ Why Other Options Are Incorrect

Option A → Includes Statement 3, which is incorrect because both components are not solutes.
Option C → Includes Statement 3 and excludes Statement 1.

3. • Option D → Excludes Statement 2, which is correct.

🎯 Strategy

Used

4. Elimination

Application:

Identify the false statement and eliminate options containing it.

Final Logic:

Smaller quantity = solute; larger quantity = solvent.

🧠 Memory Trick

1. → More = Solvent.

📚 2. Class XII – Chemistry Part I – Chapter: Solutions – Topic: Solute and Solvent

3 In a binary solution containing components A and B, if the mole fraction of component A is 0.4, what reasoning logically dictates the mole fraction of component B?

A It must be 0.4 because binary solutions have equal parts.

B It must be 0.6 because the sum of mole fractions of all components in a solution is always unity.

C It depends on the molar masses of A and B.

D It depends on the temperature of the solution.

💡 Short Explanation

Sum of mole fractions is always 1. XA + XB = 1. 1. • XB = 1 − 0.4 = 0.6.

✅ Correct Answer Explanation

2. → In a binary solution, there are only two components. The sum of their mole fractions must be equal to unity. Since the mole fraction of A is 0.4, the mole fraction of B must be 1 − 0.4 = 0.6.

❓ Why Other Options Are Incorrect

Option A → Binary solutions need not have equal mole fractions.
Option C → Mole fraction depends on number of moles, not directly on molar mass alone.

3. • Option D → Mole fraction is not dependent on temperature.

🎯 Strategy

Used

4. Substitution

Application:

Substitute the given mole fraction into the formula XA + XB = 1.

Final Logic:

1 − 0.4 = 0.6.

🧠 Memory Trick

1. → Mole fractions make one whole.

📚 2. Class XII – Chemistry Part I – Chapter: Solutions – Topic: Mole Fraction

4 When solid glucose is added to liquid water to form a binary solution, which term best identifies the dynamic process occurring when particles of the solid separate and mix uniformly into the liquid?

A Sublimation

B Dissolution

C Condensation

D Crystallisation

💡 Short Explanation

Glucose particles separate from solid state. They mix uniformly in water. 1. • This process is called dissolution.

✅ Correct Answer Explanation

2. → Dissolution is the process in which solute particles separate and become uniformly distributed in the solvent. When solid glucose is added to water, glucose molecules disperse throughout the water to form a homogeneous solution.

❓ Why Other Options Are Incorrect

Option A → Sublimation is conversion of solid directly into gas.
Option C → Condensation is conversion of gas into liquid.

3. • Option D → Crystallisation is formation of solid crystals from solution.

🎯 Strategy

Used

4. Contextual/Tonal Matching

Application:

Focus on the phrase "solid particles separate and mix uniformly into liquid."

Final Logic:

Solid solute mixing uniformly in solvent = dissolution.

🧠 Memory Trick

1. → Dissolve = Disappear uniformly.

📚 2. Class XII – Chemistry Part I – Chapter: Solutions – Topic: Dissolution of Solute

5 For a gaseous binary mixture of oxygen and nitrogen, which of the following units is most useful for relating the partial pressure of a gas to its concentration in calculations involving gas mixtures?

A Molarity (mol L⁻¹)

B Mole fraction

C Mass by volume percentage

D Molality (mol kg⁻¹)

💡 Short Explanation

Mole fraction is useful for gas mixtures. Partial pressure is related to mole fraction. 1. • It is dimensionless and composition-based.

✅ Correct Answer Explanation

2. → In gaseous mixtures, the partial pressure of a gas is directly related to its mole fraction. According to Dalton's law, partial pressure of a component depends on its mole fraction in the mixture. Therefore, mole fraction is the most suitable concentration unit for gaseous binary mixtures.

❓ Why Other Options Are Incorrect

Option A → Molarity depends on volume of solution and is mainly used for liquid solutions.
Option C → Mass by volume percentage is not suitable for partial pressure calculations.

3. • Option D → Molality uses mass of solvent and is not commonly used for gas mixture pressure relations.

🎯 Strategy

Used

4. Dimensional/Unit Analysis

Application:

Choose the unit that directly connects composition with pressure in gases.

Final Logic:

Partial pressure ∝ mole fraction.

🧠 Memory Trick

1. → Gas pressure follows mole fraction.

📚 2. Class XII – Chemistry Part I – Chapter: Solutions – Topic: Mole Fraction in Gas Mixtures

6 Identify the compound that acts as the solute in the solid-in-gas solution famously cited involving nitrogen gas.

A Palladium

B Copper

C Camphor

D Glucose

💡 Short Explanation

Camphor is a solid. Nitrogen gas acts as solvent. 1. • Camphor in nitrogen is solid-in-gas solution.

✅ Correct Answer Explanation

2. → In the example of camphor in nitrogen gas, camphor acts as the solid solute and nitrogen acts as the gaseous solvent. Since the solute is solid and the solvent is gas, it is classified as a solid-in-gas solution.

❓ Why Other Options Are Incorrect

Option A → Palladium is involved in hydrogen in palladium, a gas-in-solid solution.
Option B → Copper is commonly involved in solid alloys.

3. • Option D → Glucose is a solid solute commonly dissolved in water, not the cited nitrogen gas example.

🎯 Strategy

Used

4. Contextual/Tonal Matching

Application:

Connect the known NCERT example "camphor in nitrogen gas" with solid-in-gas solution.

Final Logic:

Camphor is the solid solute in nitrogen gas.

🧠 Memory Trick

1. → Camphor floats in gas.

📚 2. Class XII – Chemistry Part I – Chapter: Solutions – Topic: Solid in Gas Solution

7 Arrange the following steps in the correct chronological order to increase the solubility of a gas (like oxygen) in a liquid solvent (like water):
(A). Increase the pressure of the gas above the liquid.
(B). The rate of gas particles striking the surface increases.
(C). The number of gaseous particles per unit volume over the solution increases.
(D). A new equilibrium is reached with a higher gas concentration in the liquid.

A (A), (C), (B), (D)

B (A), (B), (C), (D)

C (C), (A), (B), (D)

D (B), (A), (D), (C)

💡 Short Explanation

Pressure is increased first. More gas particles occupy unit volume above solution. 1. • More collisions increase dissolution until new equilibrium forms.

✅ Correct Answer Explanation

2. → Increasing the pressure of gas above a liquid increases the number of gas particles per unit volume. This increases the rate at which gas particles strike the surface of the liquid. As more gas dissolves, a new equilibrium is established with higher concentration of gas in the liquid.

❓ Why Other Options Are Incorrect

Option B → Places collision increase before increase in gas particles per unit volume.
Option C → Begins with increased gas particles before pressure is increased.

3. • Option D → Starts with surface collision before the pressure change.

🎯 Strategy

Used

4. Option Grouping

Application:

Arrange the cause-effect sequence based on Henry's law concept.

Final Logic:

Pressure ↑ → gas particles ↑ → collisions ↑ → solubility ↑.

🧠 Memory Trick

1. → Pressure pushes gas into liquid.

📚 2. Class XII – Chemistry Part I – Chapter: Solutions – Topic: Solubility of Gases and Pressure Effect

8 Why does an amalgam of mercury with sodium NOT fit into the solid-in-liquid category?

A Because mercury is a gas at room temperature.

B Because sodium acts as the liquid solvent.

C Because it is actually a liquid-in-solid solution where solid sodium is the solvent.

D Because amalgams are inherently heterogeneous mixtures.

💡 Short Explanation

Mercury is liquid. Sodium is solid. 1. • Amalgam of mercury with sodium is liquid-in-solid solution.

✅ Correct Answer Explanation

2. → In an amalgam of mercury with sodium, mercury acts as the liquid solute and sodium acts as the solid solvent. Since the final solution is based on a solid solvent, it is classified as a liquid-in-solid solution, not a solid-in-liquid solution.

❓ Why Other Options Are Incorrect

Option A → Mercury is a liquid at room temperature, not a gas.
Option B → Sodium is not the liquid solvent; it is solid.

3. • Option D → Amalgams are homogeneous solutions/alloys, not inherently heterogeneous mixtures.

🎯 Strategy

Used

4. Odd One Out

Application:

Identify the physical states of both components and eliminate scientifically incorrect statements.

Final Logic:

Mercury liquid + sodium solid = liquid-in-solid solution.

🧠 Memory Trick

1. → Amalgam = Mercury mixed in metal.

📚 2. Class XII – Chemistry Part I – Chapter: Solutions – Topic: Liquid in Solid Solution

📄 Passage

Composition of a solution can be described by expressing its concentration. The latter can be expressed either qualitatively or quantitatively. For example, qualitatively we can say that the solution is dilute, meaning it has a relatively very small quantity of solute. Alternatively, it is concentrated, meaning it has a relatively very large quantity of solute. But in real life these kinds of description can add to a lot of confusion. Thus there is a need for a quantitative description of the solution.

Based on the passage, why is describing a solution simply as "dilute" considered inadequate in real-life applications?

A Because it implies the presence of a completely pure solvent.

B Because qualitative descriptions lack precision and can lead to confusion.

C Because "dilute" strictly means the solvent is water.

D Because dilute solutions cannot reach dynamic equilibrium.

💡 Short Explanation

"Dilute" is qualitative. It does not give exact concentration. 1. • Real-life applications need quantitative description.

✅ Correct Answer Explanation

2. → The passage clearly states that qualitative descriptions such as dilute and concentrated can create confusion in real life. This is because they do not provide exact numerical concentration. Therefore, quantitative descriptions are needed for accuracy and clarity.

❓ Why Other Options Are Incorrect

Option A → Dilute does not mean pure solvent.
Option C → Dilute is not restricted to aqueous solutions.

3. • Option D → Dynamic equilibrium is not the reason mentioned in the passage.

🎯 Strategy

Used

4. Contextual/Tonal Matching

Application:

Use the passage statement that qualitative descriptions can add confusion.

Final Logic:

Qualitative terms lack precision; quantitative values avoid confusion.

🧠 Memory Trick

1. → Dilute tells less, not exact.

📚 2. Class XII – Chemistry Part I – Chapter: Solutions – Topic: Qualitative and Quantitative Concentration

📄 Passage

According to the passage, a "concentrated" solution is best defined by which of the following?

A A solution containing exactly 50% solute by mass.

B A solution that has a relatively very large quantity of solute.

C A solution where the solute determines the physical state.

D A solution that has surpassed its saturation point.

💡 Short Explanation

Concentrated is a qualitative term. It means more solute is present. 1. • It does not indicate a fixed percentage.

✅ Correct Answer Explanation

2. → The passage directly states that a concentrated solution has a relatively very large quantity of solute. It is a qualitative description and does not necessarily provide an exact numerical concentration.

❓ Why Other Options Are Incorrect

Option A → Concentrated does not specifically mean exactly 50% solute by mass.
Option C → The solvent, not the solute, generally determines the physical state of the solution.

3. • Option D → Concentrated does not necessarily mean beyond saturation point.

🎯 Strategy

Used

4. Contextual/Tonal Matching

Application:

Match the option directly with the definition given in the passage.

Final Logic:

Concentrated = relatively large quantity of solute.

🧠 Memory Trick

1. → Concentrated = More solute.

📚 2. Class XII – Chemistry Part I – Chapter: Solutions – Topic: Concentrated Solution

11 In the solution of hydrogen in palladium, how do the roles of the components align with the general definition of solutions?

A Hydrogen is the solvent because it is a gas, and palladium is the solute.

B Palladium is the solvent because the final homogeneous mixture exists in the solid state.

C Both hydrogen and palladium act as co-solvents in a gaseous state.

D Hydrogen causes the palladium to liquefy, creating a liquid solution.

💡 Short Explanation

Palladium is present as the solid solvent. Hydrogen acts as the gaseous solute. The solvent determines the physical state of the solution.

✅ Correct Answer Explanation

In a solution, the solvent determines the physical state of the final homogeneous mixture. Hydrogen dissolves uniformly in solid palladium, producing a solid solution. Therefore, palladium acts as the solvent while hydrogen acts as the solute.

❓ Why Other Options Are Incorrect

Option A → Hydrogen is the solute, not the solvent.
Option C → Solutions contain a solvent and solute; they are not co-solvents in this example.
Option D → Hydrogen does not liquefy palladium; the resulting solution remains solid.

🎯 Strategy

Used

Substitution

Application:

Identify which component determines the physical state of the solution.

Final Logic:

Solid solution ⇒ Solid solvent ⇒ Palladium.

🧠 Memory Trick

"Palladium Provides the Phase."

📚 Class XII – Chemistry Part I – Chapter: Solutions – Topic: Gas in Solid Solutions

12 Regarding solid-in-solid solutions like alloys:
1. Bronze is a mixture of copper and tin.
2. German silver is a mixture of copper, zinc, and nickel.
3. The physical state of the solvent is solid.
4. They are heterogeneous mixtures.

A 1, 2, 3

B 2, 3, 4

C 1, 4

D 1, 2, 4

💡 Short Explanation

Bronze is Cu + Sn. German silver is Cu + Zn + Ni. Alloys are homogeneous solid solutions.

✅ Correct Answer Explanation

Bronze consists of copper and tin, while German silver consists of copper, zinc, and nickel. In solid solutions, the solvent exists in the solid state. Therefore, Statements 1, 2, and 3 are correct. Statement 4 is incorrect because alloys are homogeneous mixtures.

❓ Why Other Options Are Incorrect

Option B → Includes Statement 4, which is incorrect.
Option C → Includes Statement 4 and omits Statement 2.
Option D → Includes Statement 4, which is false.

🎯 Strategy

Used

Elimination

Application:

Verify each statement individually and eliminate options containing false statements.

Final Logic:

Only Statements 1, 2, and 3 are correct.

🧠 Memory Trick

"Bronze-Tin, German-Nickel."

📚 Class XII – Chemistry Part I – Chapter: Solutions – Topic: Solid in Solid Solutions

13 A commercial bleaching solution contains 3.62% sodium hypochlorite in water by mass. What does this specifically indicate?

A 3.62 g of water is present in 100 g of sodium hypochlorite.

B 3.62 g of sodium hypochlorite is present in 100 mL of solution.

C 3.62 g of sodium hypochlorite is dissolved in 96.38 g of water to form 100 g of solution.

D 3.62 moles of sodium hypochlorite are dissolved in 1 kg of water.

💡 Short Explanation

Mass percentage is based on total solution mass. Total solution mass equals 100 g. Solute mass is 3.62 g.

✅ Correct Answer Explanation

Mass percentage (w/w) is defined as: Mass of solute / Mass of solution × 100 Therefore, a 3.62% (w/w) sodium hypochlorite solution contains 3.62 g of sodium hypochlorite in 100 g of solution. The remaining 96.38 g is water.

❓ Why Other Options Are Incorrect

Option A → Reverses solute and solvent quantities.
Option B → Represents mass by volume percentage (w/V), not mass percentage.
Option D → Represents molality, not mass percentage.

🎯 Strategy

Used

Dimensional/Unit Analysis

Application:

Identify the concentration unit as mass percentage.

Final Logic:

3.62% (w/w) = 3.62 g per 100 g solution.

🧠 Memory Trick

"% w/w = Gram in 100 Gram."

📚 Class XII – Chemistry Part I – Chapter: Solutions – Topic: Mass Percentage

14 Consider a 10% (v/v) ethanol solution in water:
1. It contains 10 mL of ethanol dissolved in water such that the total volume is 100 mL.
2. The total volume of the solution is exactly 100 mL.
3. It contains 10 g of ethanol in 100 mL of water.
4. Such volume percentage units are commonly used for liquid-in-liquid solutions.

A 1, 2, 4

B 2, 3

C 2, 4

D 1, 3, 4

💡 Short Explanation

Volume percentage uses liquid volumes. Total solution volume is 100 mL. Commonly applied to liquid-liquid solutions.

✅ Correct Answer Explanation

A 10% (v/v) solution means 10 mL of ethanol is present in a total solution volume of 100 mL. Volume percentage is specifically used for liquid-liquid solutions. Statement 3 is incorrect because it refers to grams instead of millilitres.

❓ Why Other Options Are Incorrect

Option B → Includes Statement 3, which is incorrect.
Option C → Omits Statement 1.
Option D → Includes Statement 3, which is false.

🎯 Strategy

Used

Dimensional/Unit Analysis

Application:

Check whether the concentration is expressed using volume or mass.

Final Logic:

v/v always means mL per 100 mL solution.

🧠 Memory Trick

"v/v = mL in 100 mL."

📚 Class XII – Chemistry Part I – Chapter: Solutions – Topic: Volume Percentage

15 Arrange the following solutions in decreasing order of mass by volume percentage (w/V):
1. 5 g of solute in 100 mL of solution
2. 12 g of solute in 200 mL of solution
3. 15 g of solute in 500 mL of solution
4. 8 g of solute in 100 mL of solution

A (4), (2), (1), (3)

B (4), (1), (2), (3)

C (2), (4), (1), (3)

D (1), (2), (4), (3)

💡 Short Explanation

Calculate grams per 100 mL. Compare concentrations. Arrange in decreasing order.

✅ Correct Answer Explanation

1 → 5 g/100 mL = 5% 2 → 12 g/200 mL = 6% 3 → 15 g/500 mL = 3% 4 → 8 g/100 mL = 8% Therefore, 8% > 6% > 5% > 3% Hence the correct order is (4), (2), (1), (3).

❓ Why Other Options Are Incorrect

Option B → Places 5% before 6%.
Option C → Places 6% before 8%.
Option D → Does not follow decreasing concentration.

🎯 Strategy

Used

Dimensional/Unit Analysis

Application:

Convert every solution into grams per 100 mL before comparing.

Final Logic:

8% > 6% > 5% > 3%.

🧠 Memory Trick

"Convert First, Compare Next."

📚 Class XII – Chemistry Part I – Chapter: Solutions – Topic: Mass by Volume Percentage

16 Match the clinical scenario with its relevant concept:

List 1 (Clinical Scenario)	List 2 (Relevant Concept)
1. Intravenous injections	a. 0.9% (mass/volume) NaCl
2. Mass by volume %	b. Must match blood plasma ionic concentrations
3. Normal saline solution	c. Water retention in tissue cells
4. Edema	d. Mass of solute per 100 mL solution

A 1-b, 2-d, 3-a, 4-c

B 1-d, 2-b, 3-a, 4-c

C 1-a, 2-c, 3-d, 4-b

D 1-b, 2-a, 3-d, 4-c

💡 Short Explanation

IV injections must be isotonic with blood plasma. Mass by volume % means mass per 100 mL solution. 1. • Normal saline is 0.9% NaCl solution.

✅ Correct Answer Explanation

2. → Intravenous injections must match blood plasma ionic concentrations to avoid damage to blood cells. Mass by volume percentage means the mass of solute dissolved per 100 mL of solution. Normal saline solution contains 0.9% (mass/volume) NaCl. Edema refers to water retention in tissue cells.

❓ Why Other Options Are Incorrect

Option B → Intravenous injections and mass by volume % are incorrectly interchanged.
Option C → All major matches are incorrectly paired.

3. • Option D → Mass by volume % and normal saline solution are incorrectly interchanged.

🎯 Strategy

Used

4. Option Grouping

Application:

First match fixed definitions such as normal saline and mass by volume %, then match the clinical conditions.

Final Logic:

IV = plasma match; w/V = mass per 100 mL; saline = 0.9% NaCl; edema = water retention.

🧠 Memory Trick

1. → Saline 0.9, Edema Water.

📚 2. Class XII – Chemistry Part I – Chapter: Solutions – Topic: Clinical Applications of Concentration Units

17 Identify the concentration term best suited for expressing the amount of dissolved oxygen in seawater (approx. 5.8 g per 10⁶ g of seawater).

A Mole fraction

B Molarity

C Parts per million (ppm)

D Volume percentage

💡 Short Explanation

ppm is used for very small concentrations. Dissolved oxygen in seawater is present in trace amount. 1. • 5.8 g per 10⁶ g corresponds to ppm expression.

✅ Correct Answer Explanation

2. → Parts per million is used to express concentration when the solute is present in very small or trace amounts. Since dissolved oxygen is given as 5.8 g per 10⁶ g of seawater, it directly fits the ppm definition.

❓ Why Other Options Are Incorrect

Option A → Mole fraction is useful but not the most direct unit for the given "per 10⁶ g" expression.
Option B → Molarity depends on volume in litres, which is not given here.

3. • Option D → Volume percentage is used for volume-based liquid mixtures, not trace mass concentration.

🎯 Strategy

Used

4. Dimensional/Unit Analysis

Application:

Identify the concentration expression based on "per 10⁶" quantity.

Final Logic:

Parts per 10⁶ = parts per million.

🧠 Memory Trick

1. → ppm = per million.

📚 2. Class XII – Chemistry Part I – Chapter: Solutions – Topic: Parts Per Million

18 When atmospheric pollutants uniformly mix into the air, creating a mixture often measured in ppm, what type of general physical process has occurred?

A Chemical reaction forming a new compound

B Physical dispersion creating a homogeneous gaseous solution

C Crystallization of solid particulates

D Precipitation of gases into liquids

💡 Short Explanation

Air is a gaseous mixture. Pollutants may disperse uniformly. 1. • This forms a homogeneous gaseous solution.

✅ Correct Answer Explanation

2. → When atmospheric pollutants uniformly mix with air, no new compound is necessarily formed. The pollutants are physically dispersed throughout the gaseous medium, producing a homogeneous gaseous solution. Such trace concentrations are commonly expressed in ppm.

❓ Why Other Options Are Incorrect

Option A → Uniform mixing of pollutants does not necessarily involve a chemical reaction.
Option C → Crystallization refers to formation of crystals, not gas mixing.

3. • Option D → Precipitation refers to separation from solution, not uniform mixing in air.

🎯 Strategy

Used

4. Contextual/Tonal Matching

Application:

Focus on the terms "uniformly mix" and "air."

Final Logic:

Uniform gas mixing = homogeneous gaseous solution.

🧠 Memory Trick

1. → Pollutants disperse, not react.

📚 2. Class XII – Chemistry Part I – Chapter: Solutions – Topic: Gaseous Solutions and ppm

19 Which of the following units calculates concentration using the mass of the solvent in kg, ensuring it remains unaffected by temperature changes?

A Molarity (mol L⁻¹)

B Mole fraction (dimensionless)

C Molality (mol kg⁻¹)

D Mass percentage (% w/w)

💡 Short Explanation

Molality uses kg of solvent. Mass does not change with temperature. 1. • Therefore, molality is temperature independent.

✅ Correct Answer Explanation

2. → Molality is defined as the number of moles of solute dissolved per kilogram of solvent. Since it depends on mass of solvent rather than volume of solution, it remains unaffected by temperature changes. Hence, molality is the correct unit.

❓ Why Other Options Are Incorrect

Option A → Molarity depends on volume of solution, which changes with temperature.
Option B → Mole fraction is temperature independent but does not use kg of solvent.

3. • Option D → Mass percentage is temperature independent but does not use kg of solvent.

🎯 Strategy

Used

4. Dimensional/Unit Analysis

Application:

Identify which unit specifically contains "kg of solvent" in its definition.

Final Logic:

mol kg⁻¹ = molality.

🧠 Memory Trick

1. → Molality = moles per kg.

📚 2. Class XII – Chemistry Part I – Chapter: Solutions – Topic: Molality

20 Why is molarity considered a function of temperature?

A Because the molar mass of the solute expands with heat.

B Because it depends on the volume of the solution, which changes with temperature.

C Because mass changes dynamically with atmospheric pressure.

D Because heat causes spontaneous dissociation of all solutes.

💡 Short Explanation

Molarity uses volume of solution. Volume changes with temperature. 1. • Therefore, molarity changes with temperature.

✅ Correct Answer Explanation

2. → Molarity is defined as moles of solute per litre of solution. Since volume expands or contracts with temperature, the value of molarity can change when temperature changes. Therefore, molarity is considered temperature dependent.

❓ Why Other Options Are Incorrect

Option A → Molar mass does not expand with heat.
Option C → Mass does not change dynamically with atmospheric pressure in this context.

3. • Option D → Heat does not cause spontaneous dissociation of all solutes.

🎯 Strategy

Used

4. Dimensional/Unit Analysis

Application:

Identify the variable in molarity that changes with temperature.

Final Logic:

Molarity uses volume; volume changes with temperature.

🧠 Memory Trick

1. → Molarity moves with temperature.

📚 2. Class XII – Chemistry Part I – Chapter: Solutions – Topic: Temperature Dependence of Molarity

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