Question

Consider the combustion of butane, C4H1O: C4H10(g) + 13/2 O2(g) -> 4 CO2 (g) + 5 H2O(l). Calculate delta G

Answer 1

From internet (http://www.wiredchemist.com/chemistry/data/bond_energies_lengths.html)

, BE of C-H bond = 411 kJ,

                            C-C        "       = 346

                            O-O        "       142

                            O=O       "       494

   C-O    " 358

   C=O    " 799

   O-H    "    459   

C4H10(g) + 13/2 O2(g) -> 4 CO2 (g) + 5 H2O(l).

delta G = BE of C4H10 + 13/2*(BE of O2) - 4*BE of CO2 - 5*BE of H2O

           = ( 3*BE of C-C bond + 10*BEof C-H bond ) + 13/28(BE of O =O ) - 4 ( 2* BE of C=O bond ) - 5*(2* BE of O-H bond )

           = (3*346 + 10* 411 ) - 8 *799 - 10*459   = -5834   KJ