Question

For the reaction below CHy CH a. Estimate the gas phase enthalpy change using bond dissociation enthalpies from the OWL. Table Reference, not data from your text. button and then click the Tables link on the drop-down that appears. Include algebrakc sign and units b. Is the reaction exothermic or endothermic? c. Is the reaction likely to proceed spontaneously in the direction written? Submit Answer Retry Entire Group 1 more group attempt remaining 1 For the reaction below: a. Estimate the gas phase enthalpy change using bond dissociation enthalpies from the OWL Table Reference, not data from your text. C buton and then click the Tables link on the drop-down that appears. Include algebraic sign and units. b. Is the reaction exothermic or endothermic? c. Is the reaction likely to proceed spontancously in the direction written? Submt Answer Retry Entire Group more group atempt remaining For the reaction below a. Estimate the gas phase enthalpy change sing bond dissociation enthalpies from the OWL. Table Reference, not data from your text. button and then click the Tables link on the drop-down that appears. Include algebraic sign and units b. Is the reaction exothermic ar endothermic? c. Is the reaction likely to proceed spontaneously in the direction written? Submit Answer Retry Entire Group1 1 more group attempt remaining Cl Br OH 385 (92) N CH CH3CH2 356(85). 377(90- 368 (88) CN Clly 439 (105) 452 (108) 356185) 293 (70) 238 (57) sio (122) CHCH2 423 (101) 444 (106) 335(80) 285 68) 28 (53) 380 (91356 (85) 368 (88) 351(84) 339 (81) 305 (73) 336 (80) (CH3)2CH409 (98)448 (107) 339 (81) 27465) 226 (54) 385 (92) (CH3)3C404 (97) 331 (79) 263 (63) 213 (51) 380 (91) CH2 CHCH2. I 362 (86.5) 289 (69) 23055) 172(41) 301 (72) 243 (58) 201 (48) 368 (87) CH 376 (90) 332 (79) CH2 CH 465(11) 259 (62) 106 (97) 36 (128) 10 473 ( i 13) | 527 ( 126) | 402 (96) | 3371 80.5) | 274 (65) | 464 ( 111) | 427/ 102) 377 (90) CH30-436 (104) 333 (80) 435 1042) 5869 136) 431 (103)36 (65) 297 (71) 498 119) 49 107) 409 105) 423 102)1 543 0230 H- Most data from CRC handboak of Chemistry and Physics, 85th ed D. R Lide, ed, CRC press, Boca Raton, FL, 2001, p9 65 Uncertainties range from less than 1 kI/mol to ca. 20k/mol (5kcal/mol) and are listed in the CRC handbook Additional Bond Dissoclation Energies kJ/mol (kcal/mol) Bond D298 Bond D298 Bond D298 Bond D298 F-F 159 (38) tBu-Bu 159 (38) HC-CH 965 (231) (CH3)3Si H 378 (90) CI-CI 243 (58) 00 498 (119) HC C-H 556 (133) (CH3)3Ge-H 340 (81) Br-Br 192 (46) 0c-0 732 (175) Cl-3294) BuySn-H 308 (74) 1 151 (36) H-0 732 (175) CH3CO-H374 (89) CH3S-H 365 (87)

Answer 1

CH 2 + H-Cl Bond enthalpy of C-H bond 376 kJ/mol Bond enthalpy of H-Cl bond=431 kJ/mol In this reaction, C-H bond is broken, so bond enthalpy is positive- +376 kJ/mol H-Cl bond is formed, so the bond enthalpy is negative431 kJ/mol Hr eergy given to break bonds+ energy release for forming bonds Since the enthalpy change is positive, the energy is absorbed in the reaction -(376)-431--55 kJ/mol So it is Exothermic reaction. c) the spontaneity of the reaction depends of Gibbs Free energy which depends on enthalpy and entropy. As the reaction is gas phase reaction, there will be a very small change in the entropy. So Free energy more depends on enthalpy. Since the enthalpy is negative, Gibbs free energy will be negative and the reaction is spontaneous. YES, The reaction is spontaneous in the direction written

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+ H-Cl Bond enthalpy of C-H bond 439 kJ/mol Bond enthalpy of C-Cl bond 243 kJ/mol Bond enthalpy of C-Cl bond 356 kJ/mol Bond enthalpy of H-CI bond -431 kJ/mol In this reaction, C-H bond is broken, so bond enthalpy is positive- +439 kJ/mol Cl-Clbond is broken, so bond enthalpy is positive- 243 kJ/mol C-Cl bond is formed, so the bond enthalpy is negative-- 356 kJ/mol H-Cl bond is formed, so the bond enthalpy is negative-431 kJ/mol AHrxn-energy given to break bonds + energy release for forming bonds - + 439 + 243- 356-431- -105 kJ/mol Since the enthalpy change is positive, the energy is absorbed in the reaction. So it is Exothermic reaction. c) the spontaneity of the reaction depends of Gibbs Free energy which depends on enthalpy and entropy. As the reaction is gas phase reaction, there will be a very small change in the entropy. So Free energy more depends on enthalpy Since the enthalpy is negative, Gibbs free energy will be negative and the reaction is spontaneous. YES, The reaction is spontaneous in the direction written

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+ H-Br Bond enthalpy of C-Br bond 293 kJ/mol Bond enthalpy of H-OH bond 498 kJ/mol Bond enthalpy of C-OH bond = 385 kJ/mol Bond enthalpy of H-Cl bond 368 kJ/mol In this reaction, C-Br bond is broken, so bond enthalpy is positive-293 kJ/mol H-OH bond is broken, so bond enthalpy is positive = + 498 kJ/mol C-Cl bond is formed, so the bond enthalpy is negative-- 385 kJ/mol H-Br bond is formed, so the bond enthalpy is negative 368 kJ/mol Hrxn energy given to break bonds+energy release for forming bonds 293 + 498-385-368-+38 kJ/mol Since the enthalpy change is positive, the energy is absorbed in the reaction. So it is Endothermic reaction. c) the spontaneity of the reaction depends of Gibbs Free energy which depends on enthalpy and entropy. As the reaction is gas phase reaction, there will be a very small change in the entropy. So Free energy more depends on enthalpy. Since the enthalpy is positive, Gibbs free energy will be positive and the reaction is non-spontaneous. NO, The reaction is non-spontaneous in the direction written