JEE Main 2026 — Apr 4, Shift 2 — Physics solution

JEE Main2026Apr 4, Shift 2Physics

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 H $_{2}$ and O $_{2}$ molecules, kept in two different sized containers are same, then their temperatures will be same.

Reason R: The r.m.s. speed of H $_{2}$ and O $_{2}$ molecules are same at same temperature.

Choose the correct answer from the options given below:

A
Both A and R are true and R is the correct explanation of A
B
Both A and R are true but R is NOT the correct explanation of A
C
A is true but R is false
D
A is false but R is true

Solution

Assertion: Average translational kinetic energy per molecule is $\frac{f}{2} k_{B} T$ , which depends only on temperature (not on container size or molecular identity). Equal average KE therefore implies equal temperature. True.

Reason: $v_{r m s} = \frac{3 R T}{M}$ . Since H $_{2}$ and O $_{2}$ have different molar masses, their rms speeds at the same temperature are different. False.

$∴$ A is true but R is false.

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