📘 Solutions Class -12 – NEET के लिए Full Chapter Summary

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📘 Solutions – NEET के लिए Full Chapter Summary

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🔹 1. Types of Solutions

• Binary Solution = Solute + Solvent
  Example: Sugar in water

• Types based on states:

  • Gas in gas (air)

  • Gas in liquid (CO₂ in soda)

  • Liquid in liquid (alcohol + water)

  • Solid in liquid (salt in water)

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🔹 2. Concentration Terms

Term	Formula	Units
Mass %	$\frac{\text{mass of solute}}{\text{mass of solution}} \times 100$	%
Mole fraction (χ)	$\frac{n_{\text{solute}}}{n_{\text{solute}} + n_{\text{solvent}}}$	Unitless
Molarity (M)	$\frac{\text{mol of solute}}{\text{L of solution}}$	mol/L
Molality (m)	$\frac{\text{mol of solute}}{\text{kg of solvent}}$	mol/kg

NEET Tip: Confuse मत होना – molarity = volume-based, molality = mass-based (temperature independent!)

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🔹 3. Solubility

• Depends on nature of solute & solvent + temperature

• Solid in liquid: solubility ↑ with temp

• Gas in liquid: solubility ↓ with temp, ↑ with pressure

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🔹 4. Henry’s Law

$$P = k_H \cdot x$$

• $P$: partial pressure of gas

• $x$: mole fraction of gas in liquid

• $k_H$: Henry's constant

NEET Trick: Higher pressure → more gas dissolves

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🔹 5. Raoult’s Law

$$P_{solution} = X_A P^0_A + X_B P^0_B$$

• For ideal solutions: obey Raoult’s law at all concentrations

• For non-ideal: show +ve or –ve deviation

+ve deviation = weak interactions
–ve deviation = strong interactions

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🔹 6. Ideal & Non-Ideal Solutions

Type	Behavior	Example
Ideal	No ΔHmix, no ΔVmix	benzene + toluene
Non-Ideal	ΔHmix ≠ 0, ΔVmix ≠ 0	ethanol + water

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🔹 7. Colligative Properties (Depend on number of solute particles)

(i) Relative Lowering of Vapour Pressure

$$\frac{P^0 - P}{P^0} = \chi_{\text{solute}}$$

(ii) Elevation of Boiling Point

$$\Delta T_b = K_b \cdot m$$

(iii) Depression of Freezing Point

$$\Delta T_f = K_f \cdot m$$

(iv) Osmotic Pressure

$$\pi = CRT$$

NEET Tip: Osmotic pressure का formula सबसे ज्यादा पूछा जाता है numericals में

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🔹 8. Van’t Hoff Factor (i)

Used for association/dissociation in solutions:

$$i = \frac{\text{observed colligative property}}{\text{expected colligative property}} = \frac{\text{normal molar mass}}{\text{observed molar mass}}$$

• For NaCl, i ≈ 2

• For glucose, i = 1 (no dissociation)

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🔹 9. Abnormal Molar Mass

Occurs due to association/dissociation
Use Van’t Hoff factor to adjust

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📌 NEET Important Concepts

• Molarity vs molality comparison

• Numericals on $\Delta T_f, \Delta T_b, \pi$

• Ideal vs non-ideal solutions

• Raoult’s law graphs

• Henry’s law in respiration & scuba diving

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