Chemistry

[bravedodo12345]

Can someone please explain to me Le Chatelier's principle? I'm struggling to understand it :/

[Judes]

Le chatelier’s principle helps you predict which direction the equilibrium will shift. It tends to shift towards the direction that minimises the change. For example if you had the equation: N₂O₄ <—>2 NO₂

And you suddenly increase the concentration of N₂O₄, that would make the system suddenly shift towards the left (where the reactants are) because now we have more reactants [N₂O₄]so by Le Chatelier’s principle, we can predict that the system will shift towards the right (products) to balance out that increased concentration of the products until a new equilibrium is established


Hope that helped

[jazcstuart]

Hi!
Just to add to Judes great answer, Le Chatlier's Principle applies only to reversible reactions, which have a point of equilibrium. So for any change made, the system responds to counteract the change by shifting the equilibium, to favour either the reactants or products. There are a few different factors which affect the equilibrium of a system:

1. Temperature - if the system is exothermic in the forward direction, increasing the temperature will shift the equilibrium to favour the products according to LCP, and if the temperature is decreased the equilibrium shifts to favour the reactants. It is the opposite if the system is endothermic. You can imagine this by writing "heat" in the equation, eg. for an exothermic reaction: reactants <---> products + heat. This shows that if you add heat the system will try to minimise the heat by shifting to the left.

2. Concentration/partial gas pressure - the equilibrium shifts to favour the side with a lower total number of particles. Eg. 2X <---> 3Y + Z, if you increase the pressure the equilibrium will shift to the left as per LCP, because it has less particles so it counteracts the increase in pressure.

3. Volume (for gases) - Increasing the volume of the reaction vessel decreases the pressure because the particles are spread over a larger volume, and vice versa.

4. Adding/removing a reactant/product - adding a substance will shift the equilibrium in the opposite direction to minimise the increase in that substance, and vice versa. This is explained in Judes' answer.

Also welcome to Atar Notes both of you! Great first post Judes!

Hope this helps you understand it!