Response Of Chemical Equilibrium to Various Changes: [ENDORSED]

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If you change the concentration of a product or reactant in a reaction, the EQUILIBRIUM constant will not change!
A good way to think of this is if I have 10 M of product over two M of reactant, my chemical equilibrium constant is equal to 5! If I decide to half the amount of product and reactant, it will still equal 5 as 5/1=5. Even if I just decreased the product, or the reactant, or increased one or the other, the reaction will favor either the forward or the reverse reaction and create more or less product or reactant to then balance the reaction once again in the forward and reverse directions, and you will get the same equilibrium constant as the ratio will simplify to be equivalent to any other reaction of those specific products and reactants are given the same conditions.

A chemical reaction at equilibrium represents a fixed ratio.

Le Chatlier's Principle
>Chemical reactions will adjust to minimize the effect of changes.

Without adding more reactants, you can encourage product formation by forcing the system out of equilibrium by removing the product as its made. If you do this, more product will need to be formed to reach equilibrium, thus you can form as much product as possible and use up the reactant you have!

A change in pressure DOES not impact the equilibrium constant.
However, a change in volume, which will impact pressure does change the equilibrium constant. If all P and R are gases, then here is a shortcut method:
If volume decreases, look to see which side has the greater number of moles. If it is the left side, the reaction will shift right, as more product will be made. If it is on the right side, the reaction will shift left as more reactants will be made.

Changing Temperature of the Reaction:
This does impact K!
If the reaction is exothermic, meaning that it releases heat to the environment, and therefore delta H or enthalpy is negative, bonds are being made. If you then heat this reaction, you will be inputting heat into a system that is trying to release heat. So, you will make the reaction favor the reverse reaction.

On the other hand, there are endothermic reactions, which require an INPUT of energy to break bonds! If you heat an endothermic reaction, then you will help the reaction form more product! And the reaction will shift right.

If you COOL a reaction, you are favoring the side that has a lower enthalpy!
If you HEAT a reaction, you are favoring the side with the higher enthalpy!

[Chem_Mod]

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