Answer: 3:5.
- A 3:5
- B 5:3
- C 1:1
- D 3:7
Correct answer: A. 3:5
Explanation: U = (f/2)nRT. For equal n and T, ratio U<sub>A</sub>:U<sub>B</sub> = f<sub>A</sub>:f<sub>B</sub> = 3:5 (monatomic f=3, diatomic f=5).
Not all gas molecules move at the same speed - the Maxwell-Boltzmann distribution shows the spread, with the most probable speed vp slightly less than the average vavg, which is slightly less than the root-mean-square speed vrms used in the pressure formula.
Concept context
Kinetic theory of gases connects molecular motion to pressure and temperature, explaining gas laws, specific heats, and molecular speeds.