Answer
$\Delta H^o = -1234.76kJ$
Work Step by Step
As we found in 5.79a, the balanced equation is:
$C_2H_5OH (l) + 3O_2(g) --> 2CO_2(g) + 3H_2O(g)$
$\Delta^o_f : C_2H_5OH (l) = -277.7kj/mol$
$\Delta^o_f : O_2 (g)= 0kj/mol$
$\Delta^o_f : CO_2 (g)= -393.5kj/mol$
$\Delta^o_f : H_2O (g)= -241.82kj/mol$
*These values are given in the book
$\Delta H^o = [2*(-393.5) + 3*(-241.82) ] - [-277.7 + 3*(0)]$
$\Delta H^o = [-787 + (-725.46)] - [-277.7]$
$\Delta H^o = [-1512.46] + 277.7$
$\Delta H^o = -1234.76 kJ$
