For the reaction below: H2C-CH2 + CO + H2- CH3CH2CH Determine whether the reacti

Question

For the reaction below: H2C-CH2 + CO + H2- CH3CH2CH Determine whether the reaction is energetically favorable at room temperature. Assume that AS=0 Calculate the gas phase enthalpy change using bond dissociation enthalpies at 25°C from the table below BondDissociation Enthalpy kJ (kcal)/mol Bond Dissociation IsSocia Enthalpy kJ (kcal)/mol Bond Bond Enthalpy Bond kJ (kcal)/mol C-C 376 (90) C-N 355 (85) C-O 385 (92) C-HCH2464 (111) C 238 (57) C-Si 301 (72) H-H O-H C-H (-CH3 ) | 422 (101) 435 (104) 439 (105) C O (aldehyde)| 728 (174) C=O (CO2) | 803 (192) CEO 1075 (257) C-H (CH) | N-H Si_H 556 (133) 391 (93) 318 (76) 950 (227) 966 (231) 498 (119) C-C 727 (174) Hint: Be aware that the bond energy for the C-H bond varies considerably and may change during the reaction; therefore, you will find several entries for C-H bonds in the table Include the algebraic sign and specify units, e.g. -45 kJ/mol. Calculate to the nearest single energy unit. b. Is the reaction exothermic or endothermic?

Explanation / Answer

a)

bonds in products:

C-H = 6

C-C = 3

C=O = 1

bonds in reactants

C-H = 4

C=C = 1

C(triple)O = 1

H-H = 1

then

Hrxn = (H-H + CO + C=C +4(CH)) - (6(CH) +3CC + 1C=O)

Hrxn = (H-H + CO + C=C) - (2(CH) +3CC + 1C=O)

Hrxn = (435+1075+727) - (2*422+3*376+728)

HRxn = -463 kJ/mol

thereofre, this must be eoxthermic, since it loses energy

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