Ultraviolet photon (λ = 58.4nm) from a helium gas discharge tube is absorbed by a hydrogen molecule which is at rest. Since momentum is conserved, what is the velocity of the hydrogen molecule after absorbing the photon? What is the translational energy of the hydrogen molecule in Jmol-1. [h = 6.626 x 10-34 Js; NA = 6.022 x 1023 mol-1]

Translation energy of 1 mole of H2 molecules = KE x Avogadros number

Explanation:

Photon wavelength

Photon momentum = h/wavelength

Mass of H2 molecule m = molar mass/Avogadros number

Since momentum is conserved:

Photon momentum = H2 molecule momentum = mass x velocity of H2

velocity

Translation energy of 1 H2 molecule = kinectic energy (KE) = (1/2)mv^2

Translation energy of 1 mole of H2 molecules = KE x Avogadros number

while cooking a piece of 1/2 pound beef steak, a cast iron pan (2.4kg in weight) was heated 260 celsius.