Question

At what temperature is the rms velocity of a hydrogen molecule equal to that of an oxygen molecule at $47^\circ$C ?

• A. 80 K
• B. -73 K
• C. 3 K
• D. 20 K.

Answer 1

Answer: (D)

20 K.

Answer 2

Let $\sqrt{\frac{3Rt_r}{M_r}} = \sqrt{\frac{3Rt_0}{M_0}}$ ($\because \, rms$ velocities are same) $i.e.$ $t_r = \frac{M_r t_0}{M_0} = \frac{2}{32} \times 320$ = 20 K.