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JEE Main20264 April 2026Evening ShiftPhysicsKinetic Theory of GasesActual

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R Assertion A: If the average kinetic energy of H₂ and O₂ molecules, kept in two different sized containers are same, then their temperatures will be same. Reason R: The r.m.s. speed of H₂ and O₂ molecules are same at same temperature. Choose the correct answer from the options given below

Options

  1. ABoth A and R are true and R is the correct explanation of A
  2. BBoth A and R are true but R is NOT the correct explanation of A
  3. CA is true but R is false
  4. DA is false but R is true

Correct answer

C. A is true but R is false

Step-by-step solution

The average kinetic energy of a gas molecule is directly proportional to its absolute temperature and is given by E = f 2 k_B T , where f is the degree of freedom. Since both H₂ and O₂ are diatomic gases, they have the same degrees of freedom ( f=5 ). Therefore, if their average kinetic energies are the same, their temperatures must be the same. Thus, Assertion A is true. The root mean square (r.m.s.) speed of a gas molecule is given by v_ rms = 3RT M . Since the molar mass M of H₂ ( 2 g/mol ) is different from tha

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