Question

Helium atoms (of mass 6.65 x 10^-27 kg) are at room temperature of 20.0°C. The Boltzmann constant is 1.38 x 10^-23 J/K and Planck's constant is 6.626 x 10^-34 Js. The de Broglie wavelength of the atoms traveling at the root-mean-square speed is closest to: O 1.04 x 10^-10 m O 7.38 X 10^-10 m 3.99 X 10^-10 m o 10m O 5.22 X 10^-11 m​

Answer 1

Explanation:

Given :  T=400 K             m=4.002 amu=4.002×1.67×10−27 kg

Velocity of He atom   v=m3kT

v=4.002×1.67×10−273×1.38×10−23×400=1574 m/s

de-Broglie wavelength   λ=mvh

⟹ λ=4.002×1.67×10−27×15746.63×10−34=0.63×10−10 m