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Kinetic Theory of Gases appeared 26 times across 3 years — 3% of Physics. This question is from RMS Speed.

Year 2026 2025 2024 Total
Questions 6 11 9 26
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The r.m.s speed of oxygen molecules at 47°C is equal to that of the hydrogen molecules kept at ________ °C. (Mass of oxygen molecule / mass of hydrogen molecule = 32 / 2)

Solution & Explanation

Related Formula
Vrms = √((3RT)/(M))
Core Logic

Given that the RMS speed of oxygen molecules equals the RMS speed of hydrogen molecules:

Vrms(O₂) = Vrms(H₂) 3RTO₂MO₂ = 3RTH₂MH₂

Squaring both sides:

TO₂MO₂ = TH₂MH₂
Step 1: Absolute Temperature Conversion

Temperature of oxygen in Kelvin:

TO₂ = 273 + 47 = 320 K
Step 2: Evaluating for Hydrogen

Substitute the given mass ratio and absolute temperature:

(320)/(32) = TH₂2 10 = TH₂2 TH₂ = 20 K
Step 3: Final Conclusion

Convert back to Celsius:

TH₂ in °C = 20 - 273 = -253°C
Pattern Recognition

Direct proportionality between Temperature and Molecular Mass for equal RMS speeds. T₁/M₁ = T₂/M₂. Always convert to Kelvin before evaluating.

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_21_jan_evening

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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%)