JEE Main · Physics ↓ Falling

Kinetic Theory of Gases appeared 26 times across 3 years — 3% of Physics. This question is from Mean Free Path and Collision Frequency.

Year 2026 2025 2024 Total
Questions 6 11 9 26
Practice all Kinetic Theory of Gases questions → View full JEE Main weightage & trends →

Consider two boxes containing ideal gases A and B such that their temperatures, pressures and number densities are same. The molecular size of A is half of that of B and mass of molecule A is four times that of B. If the collision frequency in gas B is 32 × 10¹⁸/s then collision frequency in gas A is ____/s.

Solution & Explanation

Related Formula
Z = √(2)π d² N √((8RT)/(π M))

where d is molecular diameter, N is number density, T is temperature, and M is molar mass.

Core Logic

Given that T and N are identical for both gases:

Z ∝ d²√(M)

From the problem statement:

dA = (dB)/(2), MA = 4MB

Calculating the ratio of collision frequencies:

(ZA)/(ZB) = ((dA)/(dB))² × √((MB)/(MA)) = ((1)/(2))² × √((1)/(4)) = (1)/(4) × (1)/(2) = (1)/(8)

Substituting ZB = 32 × 10⁸ /s:

ZA = (32 × 10⁸)/(8) = 4 × 10⁸ /s
Step 1: Final Conclusion

The collision frequency in gas A is 4 × 10⁸ /s.

Pattern Recognition

Proportionality check: Z ∝ d² / √(M). Diameter halved 1/4 factor. Mass quadrupled 1/√(4) = 1/2 factor. Combined factor = 1/4 × 1/2 = 1/8. 32 / 8 = 4.

Chapter Mix

Class 11 Physics: Kinetic Theory of Gases

Reference Study Guides

Kinetic Theory Of Gases

More Kinetic Theory of Gases Previous-Year Questions — Page 6

Q31 jee_main_2024_31_jan_morning Kinetic Energy Of Gas Molecules
The parameter that remains the same for molecules of all gases at a given temperature is :
  • A. kinetic energy
  • B. momentum
  • C. mass
  • D. speed

Solution

Related Formula
KE = (f)/(2)kT
Core Logic

The average translational kinetic energy of any gas molecule depends only on the absolute temperature of the gas and is independent of the nature or mass of the gas.

For 1 mole of any ideal gas, the average translational kinetic energy is (3)/(2)RT. Therefore, at a given temperature, the kinetic energy parameter is uniform across all ideal gases.

Pattern Recognition

Temperature is directly proportional to average translational kinetic energy. If T is constant, KE is constant for all gases regardless of mass.

Chapter Mix

Class 11 Physics: Kinetic Theory

More Kinetic Theory of Gases Questions — jee_main_2026_22_january_evening

Practice all Kinetic Theory of Gases previous-year questions →

Rankbit System
JEE Physics: Waves (+15.5%) | Electrostatics: Concentric Shells (-29.7%) | Modern Physics: Photoelectric Clones (+34.2%) | Mathematics: Definite Integrals (+18.1%) | Chemistry: Coordination Splitting (-11.4%) | JEE Physics: Waves (+15.5%) | Electrostatics: Concentric Shells (-29.7%) | Modern Physics: Photoelectric Clones (+34.2%) | Mathematics: Definite Integrals (+18.1%) | Chemistry: Coordination Splitting (-11.4%)