Question

By using photons of specific wavelengths, chemists can dissociate gaseous HI to produce H atoms with accurately known speeds. When HI dissociates, the H atoms move away rapidly, whereas the relatively heavy I atoms move little. Use Table 9.2 in your textbook to answer the following questions: (

a) What is the longest wavelength (in nm) that can dissociate a molecule of HI?

My answer is 406 nm, and that was correct.

(b) If a photon of 243 nm is used, what is the excess energy (in J) over that needed for the dissociation?

__J

(c) If all of this excess energy is carried away by the H atom as kinetic energy, what is its speed (in m/s)?

__

I need help with b and c