Consider benzene (C6H6) in the gas phase. Write a reaction that corresponds to breaking all the carbon-carbon bonds in C6H6 (g).
The bond lengths of carbon–carbon, carbon–nitrogen, carbon–oxygen, and nitrogen–nitrogen single, double, and triple bonds are listed in Table 8.5. Plot bond enthalpy (Table 8.4) versus bond length for these bonds (as in Figure 8.17). (a) Is this statement true: “The longer the bond, the stronger the bond”? (b) Order the relative strengths of C – C, C – N, C – O, and N – N bonds from weakest to strongest. (c) From your graph for the carbon–carbon bond in part (a), estimate the bond enthalpy of the hypothetical CC quadruple bond.
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Use average bond enthalpies (Table 8.4) to estimate ∆H for the atomization of benzene, C₆H₆:
C₆H₆(g) 6 C(g) + 6 H(g)
Compare the value to that obtained by using ∆Hf° data given in Appendix C and Hess’s law. To what do you attribute the large discrepancy in the two values?
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Consider benzene (C6H6) in the gas phase. Write a reaction that corresponds to breaking all the carbon-carbon bonds in C6H6 (g).

The bond lengths of carbon–carbon, carbon–nitrogen, carbon–oxygen, and nitrogen–nitrogen single, double, and triple bonds are listed in Table 8.5. Plot bond enthalpy (Table 8.4) versus bond length for these bonds (as in Figure 8.17). (a) Is this statement true: “The longer the bond, the stronger the bond”? (b) Order the relative strengths of C – C, C – N, C – O, and N – N bonds from weakest to strongest. (c) From your graph for the carbon–carbon bond in part (a), estimate the bond enthalpy of the hypothetical CC quadruple bond.

rosewater-buffalo968

Use average bond enthalpies (Table 8.4) to estimate ∆H for the atomization of benzene, C₆H₆:

C₆H₆(g) 6 C(g) + 6 H(g)

Compare the value to that obtained by using ∆Hf° data given in Appendix C and Hess’s law. To what do you attribute the large discrepancy in the two values?

redwater-buffalo909

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