Kinetic theory of gases: formula for the most probable molecular speed Select the correct expression for the most probable speed of gas molecules in terms of absolute temperature T and molar mass M (or Boltzmann constant k and molecular mass m). Choose the correct formula.

Difficulty: Medium

Correct Answer: v_mp = √(2RT/M)

Explanation:

Concept
From the Maxwell–Boltzmann distribution for molecular speeds, the characteristic speeds are:

Verification (units)
R (J/mol·K), T (K), M (kg/mol) ⇒ RT/M has units m²/s²; square root gives m/s.

Common pitfalls
Do not confuse v_mp with v_rms (factor 3) or with v̄ (factor 8/π).

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