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? 406 nm
(b) If a photon of 299 nm is used, what is the excess energy (in J) over that needed for the dissociation? 1.76E-19 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)?
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Average Bond Energies (kJ/mol Bond Energy Bond Energy Bond Energy Bond Energy Single Bonds 347 266 327 271 218 ~170 Si-H Si-Si 323 226 368 226 565 381 310 234 N-H 432 565 427 363 295 391 160 209 201 272 200 243 159 S-H S-S H-F H-CI N-O N-F N-C S-Cl Si-F Si-Cl Si-Br 413 347 301 305 358 264 259 453 339 276 216 159 193 212 263 243 215 208 193 175 151 C-C C-Si F--F F-CI 467 351 204 265 190 203 234 234 320 213 200 490 331 272 184 O-P O-O P- Si CI CI CI-Br CI-I C-P C-F C-CI P-CI P-Br O- CI Br-I 0-I Multiple Bonds 839 891 1070 945 418 607 498 614 02 745 (799 in CO2)
