Question

At temperature T, the r.m.s. speed of helium molecules is the same as r.m.s. speed of hydrogen molecules at normal temperature and pressure. The value of T is

• A. 273°C
• B. 546°C
• C. 0°C
• D. 136.5°C

Answer 1

Answer: (A)

273°C

Answer 2

$v_{rms} = \sqrt{\frac{3RT}{M}}$Ž$E = \frac{3}{2}KT$Ž$\frac{T_{He}}{T_{H}} = \frac{M_{H}}{M_{He}}$

Ž$\frac{(273 + 0)}{T_{H}} = \frac{2}{4}$Ž$T_{H} = 546K = 273{^\circ}C$