For the reaction ABC + D ⇌ AB + CD, ΔHorxn = -38.6 kJ/mol and Ea(fwd)=297.5 kJ/mol. Assuming the reaction occurs in one step, calculate Ea(rev).

Question

For the reaction
ABC + D ⇌ AB + CD,
ΔHorxn = -38.6 kJ/mol and Ea(fwd)=297.5 kJ/mol.
Assuming the reaction occurs in one step, calculate Ea(rev). 

Please show work

Answer 1

The Ea of the forward reaction is 297.5 kJ/mole.  The E of the products is 33.6 kJ/mole LOWER than that of the reactants, hence the negative value.  Thus, the Ea of the reverse reaction requires 33.6 kJ/mole to get back to the starting point and then an additional 297.5 kJ/mole to reach the threshold.  Total = 331.1 kJ/mole.

 

If you draw the energy diagram, it will be easy to visualize/see this concept.