By using photons of specific wavelengths, chemists can dissociate gaseous Ht to

Question

By using photons of specific wavelengths, chemists can dissociate gaseous Ht to produce H atoms with accurately known speeds. When HI dissocistes, 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? 406 (b) If a photon of 242 nm is used, what is the excess energy (in J) over that needed for the dissociation? 199E2 Your response differs significantly from the correct answer. Rework your solution from the beginning and check each step carefully. (c) If all of this excess energy is carried away by the H atom as kinetic energy, what is its speed (in m/s)? m/s Average Bond Energies (k/mol) Bond Energy Bond Energy Bond Energy Bond Energy Single Bonds S-H H-Br363 218 N-Br 310 C-N C--0 213 C-Br Br-Be193 C-a 339 C-Br276 C-I Multiple Bonds N-607 745 (799 in CO C-O Table 9.2

Explanation / Answer

a) For HI--

E=h * frequency

(295*1000)/(6.022*10^23) = ((6.626*10^-34)*(3*10^8))/wavelength

wavelength = 405.78 nm

b)E=h* frequency

(6.626*10^(-34) * (3*10^8))/242*10^(-9)

.0821 * 10^(-17) J

dissociation energy = 295*1000/(6.022*10^23)

0.048*10^(-17) J

So , excess energy = .(0821 - 0.048)*10^(-17) J

0.03414 * 10^-17 J

c)

0.3414*10^(-17) = 0.5*mass of h*(velocity of h)^2

So. velocity of hydrogen atom is 20218.80313m/s

where mass of hydrogen atom is 1.67*10^(-27)Kg

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