Class 12 Chemistry MCQ Test – Solutions (Chapter 1) | Full Chapter Test

Class 12 Chemistry – Chapter: Solutions (Detailed Notes)

These notes are designed for CBSE, GSEB, JEE and NEET students. It includes detailed theory, concepts, formulas and exam-oriented explanations.

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1. What is a Solution?

A solution is a homogeneous mixture of two or more substances whose composition is uniform throughout the system. This means that any small sample taken from the solution will have the same composition and properties.

A solution consists of:

• Solvent: The component present in larger amount and determines the physical state.
• Solute: The component present in smaller amount and dissolved in solvent.

Example: In salt water, water is solvent and salt is solute.

Types of Solutions

Solutions can exist in different physical states such as gaseous, liquid and solid depending on the nature of solute and solvent.

• Gas in Gas → Air
• Gas in Liquid → Oxygen in water
• Liquid in Liquid → Alcohol in water
• Solid in Liquid → Sugar in water
• Solid in Solid → Alloys (Brass)

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2. Methods of Expressing Concentration

Concentration tells how much solute is dissolved in a given amount of solvent or solution. It is very important in chemistry as it helps in quantitative analysis.

1. Mass Percentage

It is defined as the mass of solute present in 100 g of solution.

\( \text{Mass \%} = \frac{\text{Mass of solute}}{\text{Mass of solution}} \times 100 \)

Used in industrial solutions and medicines.

2. Molarity (M)

Molarity is defined as the number of moles of solute dissolved in one litre of solution.

\( M = \frac{n}{V(\text{L})} \)

Important: Molarity depends on temperature because volume changes with temperature.

3. Molality (m)

Molality is defined as the number of moles of solute per kilogram of solvent.

\( m = \frac{n}{W(\text{kg})} \)

Molality is temperature independent because mass does not change.

4. Mole Fraction

It is the ratio of moles of one component to total moles in solution.

\( x_A = \frac{n_A}{n_A + n_B} \)

Total mole fraction is always:

\( x_A + x_B = 1 \)

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3. Solubility of Gases – Henry’s Law

The solubility of a gas in a liquid depends on pressure and temperature.

Henry’s Law: At constant temperature, the solubility of a gas is directly proportional to its partial pressure.

\( p = K_H \cdot x \)

Where:

• \( p \) = Partial pressure of gas
• \( x \) = Mole fraction of gas
• \( K_H \) = Henry’s constant

Higher value of \( K_H \) means lower solubility.

Applications:

• Scuba diving (avoiding bends)
• Carbonated drinks

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4. Vapour Pressure & Raoult’s Law

Vapour pressure is the pressure exerted by vapour in equilibrium with its liquid.

Raoult’s Law

The partial vapour pressure of each component is proportional to its mole fraction.

\( p_1 = p_1^\circ x_1 \)

\( p_2 = p_2^\circ x_2 \)

Total Pressure:

\( P = p_1^\circ x_1 + p_2^\circ x_2 \)

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5. Ideal and Non-Ideal Solutions

Ideal Solutions

• Obey Raoult’s law completely
• \( \Delta H = 0 \)
• \( \Delta V = 0 \)
• Forces between molecules are similar

Non-Ideal Solutions

• Do not obey Raoult’s law
• \( \Delta H \neq 0 \)
• Show deviation

Types of deviation:

• Positive: weaker forces → higher vapour pressure
• Negative: stronger forces → lower vapour pressure

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6. Colligative Properties

Colligative properties depend only on number of particles, not nature of solute.

1. Relative Lowering of Vapour Pressure

\( \frac{p^\circ - p}{p^\circ} = x_2 \)

2. Elevation of Boiling Point

\( \Delta T_b = K_b m \)

3. Depression of Freezing Point

\( \Delta T_f = K_f m \)

4. Osmotic Pressure

\( \pi = CRT \)

Highly important for determining molar mass of biomolecules.

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7. Van’t Hoff Factor

Sometimes solutes dissociate or associate, changing number of particles.

\( i = \frac{\text{Observed property}}{\text{Calculated property}} \)

• \( i = 1 \) → normal
• \( i > 1 \) → dissociation
• \( i < 1 \) → association

Modified Equations

\( \Delta T_b = i K_b m \)

\( \Delta T_f = i K_f m \)

\( \pi = i CRT \)

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⬇️ Attempt the test given below after revising these notes

Class 12 Chemistry

Chapter 1 : Solutions | Full Chapter MCQ Test

Time Left: 20:00

Student Name:

1. The vapour pressure of a solution containing non-volatile solute is:

greater than solvent equal to solvent less than pure solvent independent of solute

2. Raoult’s law is applicable to:

ideal solutions electrolytes only strong electrolytes colloidal solutions

3. Henry’s law constant increases with:

decrease in temperature increase in temperature pressure decrease solvent density

4. Osmotic pressure depends on:

nature of solute number of solute particles solvent type viscosity

5. Which property is NOT colligative?

Osmotic pressure Elevation of boiling point Vapour pressure lowering Density

6. Van’t Hoff factor is defined as:

observed colligative property / calculated calculated / observed temperature ratio mole fraction ratio

7. Depression in freezing point depends on:

molality molarity mole fraction normality

8. Unit of molality is:

mol L⁻¹ mol kg⁻¹ kg mol⁻¹ g mol⁻¹

9. Ideal solutions obey:

Raoult’s law Henry’s law Dalton law Boyle law

10. Positive deviation from Raoult’s law means:

weaker intermolecular forces stronger intermolecular forces no interaction ionic bonding

11. Osmotic pressure equation is:

π = CRT π = MRT π = nRT π = PV

12. Colligative properties depend on:

nature of solvent number of particles volume of solution pressure

13. If i > 1, the solute undergoes:

association dissociation polymerization neutralization

14. Example of ideal solution:

Benzene + Toluene Ethanol + Water Acetone + Water HCl + Water

15. Unit of Henry’s law constant:

atm atm⁻¹ mol K

16. Osmosis occurs through:

semi-permeable membrane filter paper glass plate metal sheet

17. Elevation in boiling point is proportional to:

molality molarity mole fraction density

18. If solute associates, Van’t Hoff factor becomes:

>1 <1 label=""> =1 0

19. Raoult's law formula:

P = X₁P₁° PV=nRT π = MRT Kb m

20. Colligative properties are useful to determine:

molecular mass density viscosity pressure

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