States of Matter
Gas laws, kinetic theory, real gases, liquids
Key Concepts
- Ideal gas: molecules have no volume or interactions; obeys PV = nRT
- Real gases deviate at high pressure and low temperature
- Kinetic theory: temperature is proportional to mean kinetic energy
- Critical temperature T_c: above this, gas cannot be liquefied by pressure alone
- Intermolecular forces: London < dipole–dipole < hydrogen bond (increasing strength)
Important Formulae
| Ideal gas law | PV = nRT (R = 8.314 J/mol·K) |
| Van der Waals equation | (P + an²/V²)(V − nb) = nRT |
| Average kinetic energy | KE_avg = 3/2 · kT |
| Boyle's law | PV = constant (T, n fixed) |
| Charles's law | V/T = constant (P, n fixed) |
| Graham's law of diffusion | r₁/r₂ = √(M₂/M₁) |
Quick Tips
- Van der Waals constant a: accounts for intermolecular attraction; b: accounts for finite molecular volume.
- At STP (0°C, 1 atm): V_molar = 22.4 L/mol; at SATP (25°C, 1 bar): V_molar = 24.8 L/mol.
- Lighter gases diffuse faster (Graham's law) — H₂ diffuses fastest.
Sample Practice Questions
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Mean free path of a gas molecule is the average distance:
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Answer: Between two successive collisions
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Unit of gas constant R:
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Answer: J mol⁻¹ K⁻¹
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Avogadro's law: equal volumes of all gases at same T and P contain:
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Answer: Equal number of molecules
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Ideal gas equation is:
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Answer: PV = nRT
Practice Questions
Practice 20 randomly selected NEET questions on States of Matter. Answers are revealed after each question.
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What are the key concepts in States of Matter for NEET?
Ideal gas: molecules have no volume or interactions; obeys PV = nRT; Real gases deviate at high pressure and low temperature; Kinetic theory: temperature is proportional to mean kinetic energy; Critical temperature T_c: above this, gas cannot be liquefied by pressure alone; Intermolecular forces: London < dipole–dipole < hydrogen bond (increasing strength).
Which formulae are important for States of Matter in NEET?
Ideal gas law: PV = nRT (R = 8.314 J/mol·K); Van der Waals equation: (P + an²/V²)(V − nb) = nRT; Average kinetic energy: KE_avg = 3/2 · kT; Boyle's law: PV = constant (T, n fixed); Charles's law: V/T = constant (P, n fixed); Graham's law of diffusion: r₁/r₂ = √(M₂/M₁).
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