Be sure to answer all parts. The average C-H bond energy in CH4 is 415 kJ/mol. U

Question

Be sure to answer all parts. The average C-H bond energy in CH4 is 415 kJ/mol. Use the following data to calculate the average C-H bond energy in ethane (C2Hs C-C bond), in ethene (C2H4 C-C bond), and in ethyne (C2H23 C bond). (1) C2H6(g)-H (g) 2 CH4(g) AHo,'-65.07 kJ/mol rKIn (2) C2H4(g) 2 H (g) 2 CH4(g) AHo --202.21 kJ/mol , rKIn (3) C2H2(g) 3 H (g) 2 CH4(g) AHo -376.74 kJ/mol rKIn Average C-H bond energy in ethane- Average C-H bond energy in ethene- Average C-H bond energy in ethyne = kJ/mol kJ/mol kJ/mol Average bond energies (kJ/mol) Bond Energy H 432 413 C-C 347 C-N305 C-o358 614 745 2C1 839 C01,070 498 C=C C-O 02

Explanation / Answer

1)

   DHrxn = 6*DH0d,C-H + DH0d,C-C + DH0d,H-H + 8*DH0d,C-H

   -65.07 = 6*X+347+432+8*(-413)

average C-H bond enrgy in C2H6 = 409.98 Kj/mol

2) DHrxn = 4*DH0d,C-H + DH0d,C=C + 2*DH0d,H-H + 8*DH0d,C-H

   -202.21 = 4*X + 614 + 2*432 + 8*(-413)

average C-H bond enrgy in C2H4 = 405.95 Kj/mol

3) DHrxn = 2*DH0d,C-H + DH0d,C,Ctriple bond + 3*DH0d,H-H + 8*DH0d,C-H

   -376.74 = 2*X + 839 + 3*432 + 8*(-413)

average C-H bond enrgy in C2H4 = 396.13 Kj/mol

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