Q.

At what temperature will the rms speed of oxygen molecules become just sufficient for escaping from the Earth's atmosphere

(Given: Mass of oxygen molecule (m)=2.76×10-26kg, Boltzmann’s constant kB=1.38×10-23J K-1)              [2018]

1 2.508×104 K  
2 8.360×104 K  
3 5.016×104 K  
4 1.254×104 K  

Ans.

(2)

Escape velocity from the Earth's surface is 

vescape=11200m s-1

Say at temperature T, oxygen molecule attains escape velocity.

So, vescape=3kBTmO211200=3×1.38×10-23×T2.76×10-26

On solving,  T=8.360×104 K