How do bond energies help assess the thermodynamics of a reaction?

Question

A)They provide a way to estimate the activation energy of the reaction
B) They provide a way to determine the equilibrium constant
C) They provide a way to estimate delta G.
D) They provide a way to estimate " H
E) They provide a way to estimate " S

Answer 1

Let's start by figuring out what bond energies can do, by looking at a simple reaction:
CH4 + 2O2 ---> CO2 + 2H2O

Step 1: Find the # of bonds, and the bond energies, then determine the total bond energies for the reactants and products.

Reactants:
4 C-H bonds (413 kJ/mol)
2 O=O bonds (498 kJ/mol)
Total: 2648 kJ/mol

Products:
4 O-H bonds (366 kJ/mol)
2 C-O bonds (360 kJ/mol)
Total: 2184 kJ/mol

Step 2: Subtract the product's energy from the reactant's energy to determine ΔH.
ΔH = 2648 - 2184 = 464 kJ/mol gained from the reaction.

So we've determined ΔH (enthalpy) (d).

A table of common bond energies is below.