Calculate the average speed of helium atoms at 300 K.

Uav=8kTπm1/2Substituting the value of k=1.381×10−23kgm2s−2K−              T=300K,π=3.14m=4.0×1.66×10−27kg                            (∵ at. wt. of He = 4)  in the above equation, we get : Uacg=8×1.381×10−23kgm2s−2K−×300K3.14×4×1.66×10−27kg1/2=1589671m2s−21/2=1260.8ms−