The r.m.s. speed of particle of mass 5×10−17 kg in their random motion in air at NTP will be (Boltzmann's constant) K=1.38×10−23J/K:

GivenMass of the particle m=5×10−17kg.Absolute temperature = 273 KThe rms speed of the particle is given by           vrms=3KTm=3×1.38×10−23×2735×10−17      =226×10−6=15×10−3m/s