1. NCERT Definitions (Commonly asked in 1 mark)

Solution: A homogeneous mixture of two or more than two substances.
Solvent: The component of a solution present in the largest amount.
Solute: The component of a solution present in a lesser amount than the solvent.
Gaseous Solutions: Solution where the solvent is the gas. For example, Mixture of oxygen and nitrogen gases.
Liquid Solutions: Solutions where the solvent is a liquid. They can contain solid, liquid, or gas as solutes. For example, Oxygen dissolved in water.
Solid Solutions: Solutions where the solvent is a solid. These are typically mixtures of metals, known as alloys, like brass (Copper and Zinc).
Molarity (M): A concentration measure defined as the number of moles of solute per litre of solution.
Molality (m): A concentration measure defined as the number of moles of solute per kilogram of solvent.
Mole Fraction: A concentration measure defined as the ratio of the number of moles of a component to the total number of moles of all the components present in the solution.

2. Important Facts

Mass percentage is commonly used in industrial chemical applications.
Volume percentage is often used for solutions containing liquids.
Mass by volume percentage is frequently used in medicine and pharmacy.
A concentration term used when solute is present in trace quantities is ~Parts per million.
Parts per million (ppm) is used to measure concentration of pollutants in water and air.
Mass %, ppm, mole fraction and molality are independent of temperature.
A concentration term which is a function of temperature is ~Molarity.

3. Classification: Types of Solutions

On the basis of physical states of solute and solvent:

Type of Solution	Solute	Solvent	Common Examples
Gaseous Solutions	Gas	Gas	Mixture of oxygen and nitrogen gases
	Liquid	Gas	Chloroform mixed with nitrogen gas
	Solid	Gas	Camphor in nitrogen gas
Liquid Solutions	Gas	Liquid	Oxygen dissolved in water
	Liquid	Liquid	Ethanol dissolved in water
	Solid	Liquid	Glucose dissolved in water
Solid Solutions	Gas	Solid	Solution of hydrogen in palladium
	Liquid	Solid	Amalgam of mercury with sodium
	Solid	Solid	Copper dissolved in gold

4. Important Formulae (Concentration)

1. Mass percentage (w/w):	Mass % of a component = (Mass of the component in the solution / Total mass of the solution) × 100
2. Volume percentage (V/V):	Volume % of a component = (Volume of the component / Total volume of solution) × 100
3. Parts per million (ppm):	(Number of parts of the component / Total number of parts of all components of the solution) × 10⁶
4. Mole fraction of a component (χ):	Number of moles of the component / Total number of moles of all the components
5. Molarity (M):	Moles of solute / Volume of solution in litre
6. Molality (m):	Moles of solute / Mass of solvent in kg

5. Real Life Application Based Questions (Part 1)

1. Explain how the concentration of fluoride in drinking water is an application of the parts per million (ppm) concept.
Ans. Fluoride concentration in drinking water is often kept around 1 ppm to prevent tooth decay, while 1.5 ppm causes the tooth to become mottled and high concentrations of fluoride ions can be poisonous. This demonstrates how small amounts of a solute can have significant health benefits.

2. In the food industry, why is the concentration of salt in brine solutions expressed in mass percentage (w/w)?
Ans. Expressing salt concentration in mass percentage ensures uniformity in preserving food. It helps in achieving the right osmotic balance to inhibit microbial growth, thereby extending the shelf life of the product.

Solubility

6. NCERT Definitions (Solubility)

Solubility: Solubility of a substance is its maximum amount that can be dissolved in a specified amount of solvent at a specified temperature.
Saturated Solution: A saturated solution is a solution in which no more solute can be dissolved at a same temperature and pressure.
Unsaturated Solution: An unsaturated solution is one in which more solute can be dissolved at the same temperature.

7. Important Facts (Solubility)

Higher the value of K_H at a given pressure, the lower is the solubility of the gas in the liquid.
A principle which states that solute dissolves in a solvent if the intermolecular interactions are similar in the two is ~Like dissolves like.
The solubility of solids in liquids increases with a rise in temperature if the dissolution process is endothermic, and if it is exothermic, the solubility should decrease, while solubility of gases in liquids decreases with temperature and increases with pressure.
A condition caused due to low concentrations of oxygen in the blood and tissues is ~Anoxia.

8. Important Concepts (Solubility)

Henry's law: It states that at a constant temperature, the partial pressure of the gas in vapour phase (p) is directly proportional to the mole fraction of the gas (χ) in the solution, i.e., p = K_Hχ where, K_H is the Henry's law constant.

9. Real Life Application Based Questions (Part 2)

1. Why is carbon dioxide used in soft drinks and how does temperature affect its solubility?
Ans. Carbon dioxide is used in soft drinks for carbonation, providing fizz and a tangy taste. The solubility of CO₂ decreases with increasing temperature, causing the drink to go flat faster when warm.

2. How does the solubility of oxygen in water affect aquatic life, especially in warmer conditions?
Ans. Oxygen's solubility in water decreases with increasing temperature, which can lead to lower oxygen levels in warm water bodies. This can stress or kill aquatic organisms that rely on dissolved oxygen for survival.

3. Why do divers use a tank filled with the air diluted with helium when diving at great depths?
Ans. Scuba divers must cope with high concentrations of dissolved gases while breathing air at high pressure underwater. Increased pressure increases the solubility of atmospheric gases in blood. When the divers come towards surface, the pressure gradually decreases. This releases the dissolved gases and leads to the formation of bubbles of nitrogen in the blood. This blocks capillaries.

Vapour Pressure of Liquid Solutions & Ideal and Non-Ideal Solutions

10. NCERT Definitions (Vapour Pressure)

Binary Solution: A solution containing two components, for instance, liquid-liquid or solid-liquid mixtures.
Partial Vapour Pressure: The pressure exerted by a single component of a mixture in the vapour phase.
Ideal Solution: A solution that obeys Raoult's law over the entire range of concentration.
Non-Ideal Solution: A solution that does not obey Raoult's law over the entire range of concentration.
Azeotrope: A mixture of two liquids that has the same composition in both liquid and vapour phase and boils at a constant temperature.

11. Important Facts (Azeotropes)

A solution which shows a large positive deviation from Raoult's law: ~Minimum Boiling Azeotrope.
An example of azeotrope that has the approximate composition, 68% nitric acid and 32% water by mass, with a boiling point of 393.5 K: ~Maximum Boiling Azeotrope.
Positive deviations from Raoult's Law indicates weaker interactions between different molecules.
Negative deviations from Raoult's Law indicates stronger interactions between different molecules.

12. Important Concepts (Raoult's Law & Dalton's Law)

Raoult's Law: States that the partial vapour pressure of each component of a solution is directly proportional to its mole fraction present in the solution, that is, p = p⁰ χ₁ where p⁰ is the vapour pressure of pure component.
Dalton's Law of Partial Pressures: The total pressure over the solution phase in the container will be the sum of the partial pressures of the components of the solution, that is, P_total = P₁ + P₂.
According to Raoult's law: p₁ = p₁⁰ x₁ and p₂ = p₂⁰ x₂
Substituting the values of p₁ and p₂, we get:
P_total = x₁ p₁⁰ + x₂ p₂⁰ = (1 - x₂) p₁⁰ + x₂ p₂⁰ = p₁⁰ + (p₂⁰ - p₁⁰) x₂
If y₁ and y₂ are the mole fractions in the vapour phase then: p₁ = y₁ P_total and p₂ = y₂ P_total. In general, p_i = y_i P_total

13. Difference Between Tables

Ideal Solutions vs. Non-Ideal Solutions

Aspect	Ideal Solutions	Non-Ideal Solutions
Raoult's Law	Obey Raoult's Law over the entire range of concentrations.	Do not obey Raoult's Law over the entire range of concentrations.
Change in enthalpy/ volume	No change in enthalpy or volume upon mixing (Δ_mixH = 0, Δ_mixV = 0).	Mixing may involve changes in enthalpy and volume.
Intermolecular forces	Intermolecular forces between unlike molecules are similar to those between like molecules.	Intermolecular forces between unlike molecules differ significantly from those between like molecules.
Mixing behaviour	Represent ideal mixing behaviour without energy change.	Show either positive or negative deviation based on the nature of intermolecular interactions.
Example	Benzene and toluene mixture.	Ethanol and acetone mixture (positive deviation) or chloroform and acetone mixture (negative deviation).

Positive Deviation from Raoult's Law vs. Negative Deviation from Raoult's Law

Aspect	Positive Deviation	Negative Deviation
A-B interactions	Occurs when A-B interactions are weaker than A-A or B-B interactions.	Occurs when A-B interactions are stronger than A-A or B-B interactions.
Vapour pressure	Results in a higher vapour pressure than predicted by Raoult's Law.	Results in a lower vapour pressure than predicted by Raoult's Law.
Enthalpy of mixing	Enthalpy of mixing is positive (i.e; ΔH_mix > 0)	Enthalpy of mixing is negative (i.e; ΔH_mix < 0)
Volume of mixing	Volume of mixing is positive (i.e; ΔV_mix > 0)	Volume of mixing is negative (i.e; ΔV_mix < 0)
Azeotropes	Often leads to the formation of minimum boiling azeotropes.	Often leads to the formation of maximum boiling azeotropes.
Example	Ethanol and acetone.	Phenol and aniline.

Minimum Boiling Azeotropes vs. Maximum Boiling Azeotropes

Aspect	Minimum Boiling Azeotropes	Maximum Boiling Azeotropes
Composition	Composition remains constant at boiling point, but boils at a lower temperature than either of the pure components.	Composition remains constant at boiling point, but boils at a higher temperature than either component.
Deviation from Raoult's Law	Formed by solutions showing large positive deviations from Raoult's Law.	Formed by solutions showing large negative deviations from Raoult's Law.
Example	Ethanol-water mixture.	Nitric acid-water mixture.

Colligative Properties of Solutions and Abnormal Molar Mass

14. NCERT Definitions (Colligative Properties)

Colligative Properties: Properties which depend on the number of solute particles irrespective of their nature relative to the total number of particles present in the solution.
Osmotic Pressure: The pressure required to prevent the flow of solvent into a solution through a semipermeable membrane.
Semipermeable Membrane (SPM): A membrane that allows the passage of solvent molecules but blocks solute particles.
Osmosis: The movement of solvent molecules through a semipermeable membrane from a region of lower solute concentration to a region of higher solute concentration.
Reverse Osmosis: The process by which solvent molecules are forced to move from a region of higher solute concentration to a region of lower solute concentration by applying pressure greater than the osmotic pressure.
Isotonic Solutions: Two solutions having the same osmotic pressure at a given temperature.
Hypotonic Solutions: If the salt concentration is less than 0.9% (mass/volume), the solution is said to be hypotonic.
Hypertonic Solution: If the salt concentration is more than 0.9% (mass/volume), the solution is said to be hypertonic.
Van't Hoff Factor (i): The van't Hoff factor (i) is a dimensionless quantity that represents the number of particles into which a solute dissociates or associates in a solution.

15. Important Facts (Colligative Properties)

A membrane through which only solvent molecules can pass through: ~Semipermeable Membrane.
A colligative property used for water purification: ~Reverse Osmosis.
Cryoscopic and ebullioscopic constants are unique for each solvent.
A proportionality constant used in calculating freezing point depression: ~Cryoscopic Constant.
A proportionality constant used in calculating boiling point elevation: ~Ebullioscopic Constant.

16. Important Formulae (Colligative Properties)

Relative lowering of Vapour Pressure:	Δp₁ / p₁⁰ = (p₁⁰ - p₁) / p₁⁰ = x₂ or (p₁⁰ - p₁) / p₁⁰ = n₂ / (n₁ + n₂) For dilute solutions, n₂ << n₁ : (p₁⁰ - p₁) / p₁⁰ = (w₂ × M₁) / (M₂ × w₁)
Elevation of Boiling Point:	ΔT_b = K_b m ΔT_b = (K_b × w₂ × 1000) / (M₂ × w₁)
Depression of Freezing Point:	ΔT_f = K_f m ΔT_f = (K_f × w₂ × 1000) / (M₂ × w₁)
Osmotic Pressure:	π = C R T = (n₂ / V) R T π = w₂ R T / (M₂ × V)
Van't Hoff factor, i:	i = Normal molar mass / Abnormal molar mass = Observed colligative property / Calculated colligative property

Inclusion of van't Hoff factor modifies the equations:

Relative lowering of vapour pressure: (p₁⁰ - p₁) / p₁⁰ = i × (n₂ / n₁)
Elevation of Boiling point: ΔT_b = i K_b m
Depression of Freezing point: ΔT_f = i K_f m
Osmotic pressure of solution: π = i(n₂ R T) / V

Solutions: Full Concept Mind Map Textual Representation

A. Types of Solutions

Gaseous: Gas-Gas → O₂+N₂, Liquid-Gas → Chloroform+N₂, Solid-Gas → Camphor+N₂
Liquid: Gas-Liquid → O₂ in water, Liquid-Liquid → Ethanol in water, Solid-Liquid → Glucose in water
Solid: Gas-Solid → H₂ in Pd, Liquid-Solid → Amalgam of Hg+Na, Solid-Solid → Cu in gold

B. Expressing Concentration of Solutions

Mass by volume percentage (w/V): (Mass of solute / Volume of solution) × 100
Volume percentage (V/V): (Volume of component / Total volume of solution) × 100
Mass percentage (w/w): (Mass of component in solution / Total mass of solution) × 100
Parts per million: (No. of parts of components × 10⁶ / Total no. of parts of all components of solution)
Mole Fraction: No. of moles of components / Total no. of moles of all components
Normality: No. of gram equivalent of solute × 1000 / Volume of solution (in mL)
Molality: No. of moles of solute × 1000 / Mass of solvent (in g)
Molarity: No. of moles of solute × 1000 / Volume of solution (in mL)

C. Solubility

Solid in liquid: Endothermic, Δ_sol H > 0, Solubility increases with increasing T. Exothermic, Δ_sol H < 0, Solubility decreases with increasing T. Pressure: Not significant effect.
Gas in liquid: Increases with decrease in temperature. Increases with increase in pressure. Henry's Law: p = K_Hχ.

D. Ideal and Non-Ideal Solutions & Azeotropes

Ideal Solutions: Obey Raoult's law. ΔH_mix = 0, ΔV_mix = 0. Interactions A-A and B-B = A-B.
Non-Ideal Solutions: Do not obey Raoult's law. ΔH_mix ≠ 0 and ΔV_mix ≠ 0.
- Positive Deviation: ΔH_mix > 0; ΔV_mix > 0. Interactions A-B < A-A or B-B. (Forms Minimum boiling azeotropes).
- Negative Deviation: ΔH_mix < 0; ΔV_mix < 0. Interactions A-B > A-A or B-B. (Forms Maximum boiling azeotropes).

E. Colligative Properties

Relative lowering of vapour pressure → χ₂ = (p₁⁰ - p₁) / p₁⁰
Osmotic pressure → π = C R T
Elevation of boiling point → ΔT_b = K_b × m
Depression in freezing point → ΔT_f = K_f × m

Osmotic Pressure Terms: Osmosis, Osmotic pressure, Isotonic Solutions, Hypertonic Solution (cell shrinks), Hypotonic Solutions (cell swells), Reverse Osmosis.

F. Liquid-Liquid Solutions (Raoult's Law)

Raoult's law: P₁ = P₁⁰ χ₁
Dalton's law of partial pressure: P_Total = P₁ + P₂ + ... P_n
In vapour phase, P₁ = y₁ P_Total

G. Abnormal Molecular Mass

van't Hoff factor (i) = Normal molar mass / Abnormal molar mass = Observed Colligative Property / Calculated Colligative Property.
i = 1 : Neither association nor dissociation.
i < 1 : Association in solution.
i > 1 : Dissociation in solution.

Types of Solutions and Expressing Concentration of Solutions