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The Haber process question

The forward reaction is exothermic so why does lowering the energy of the system create more products?

Please don't make the answer in terms of le chateliers principle b🙂

Here's my thoughts: when you add heat the reactants absorb more energy and thus more reactant bonds break; these broken-up particles then collide and react to form new molecules and energy is released 🙂

Reply 1

HelloHello!

Le chatelier is not as hellish as you think.
Exothermic = releases energy.
This is a change of the eqm.

Therefore if you lower the energy, to oppose this....
the forward reaction is favoured therefore more products :smile:

Reply 2

HelloHello!

When the temperature/energy of an equilibrium is increased, the rate of both the forward and back reaction is increased. However the rate of the forward exothermic reaction is increased more.

rate=Ae^*(-Ea/RT)
can be used to verify this

Reply 3

Kian Stevens

This question can only be answered with Le Chatelier's principle...

What is Le Chatelier's principle? 'If a system in dynamic equilibrium experiences a change, the equilibrium will shift to oppose that change'. So if the forward reaction is exothermic, and the energy of the system increases, the equilibrium will shift in the endothermic direction to oppose the change. The opposite is true when the energy of the system is decreased.

Reply 4

charco

Study Forum Helper

Original post by Kian Stevens

It all depends which board you are studying. Le Chatelier cannot be used as an explanation for IB students, as they say that it is an empirical guide, not an explanation.

Increasing the temperature increases the rate of both forward and reverse reactions.

But the endothermic reaction has a higher activation energy and the rate in the endothermic direction increases more than the rate in the exothermic direction and this disturbs the equilibrium in the direction of endothermic change.

This can be shown using a Maxwell - Boltzmann distribution, where the proportional increase in particles able to react is more pronounced for the higher activation energy.

When equilibrium is re-established at the higher temperature there will be more of the endothermic product and less of the exothermic product.

Reply 5

Freedom physics

Thanks for the help! I went through both of the main equilibrium constants and figured out that le chatelier's principle works because of the equilibrium constants and there's no explanation in A-level to why the equilibrium constants work other than the fact that the changes in the position of the equilibrium constant are observed if that makes sense 🙂