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When a reactant or product is added to a system at equilibrium, the system shifts away from the added component.
But if a reactant or product is removed, the system shifts toward the removed component.
What would happen if we add more
Fe3+ to the system?
How does this affect each of the reaction participants?
Sometimes we remove some of the substances by adding another substance that reacts with a participant in a side reaction.
What happens if we remove some SCN-?
If you add reactants (or increase their concentration).
Reactants Products
If you add products (or increase their concentration)
The opposite will occur
Equilibrium “Shifts to the left”
Reactants Products
****Note: Le Chatelier's Principle does not apply to pure solids or pure liquids***
Changes in volume are going to have the opposite affect of changes in pressure
Example:
Increase volume (therefore decrease pressure) results in a shift to the right
For each of the following predict whether the given change will cause the equilibrium to shift in favour of the products or the reactants, or neither.
If both sides of the equation have equal number of moles, then change in pressure will have no effect on the balance of equilibrium
Example: Predict the effect on equilibrium when the pressure is increased for the following reaction:
Only applies to gases in equilibrium in a closed system
With gases, equal volumes contain equal numbers of particles (no matter what gases we are comparing)
As the pressure increases, the reaction with shift in the direction of the least gases (the number of moles)
At high pressure
At low pressure
We can think of heat as a "reactant" for endothermic reactions
Or a "product" for exothermic reactions
For this example: an increase in temperature will favor the forward reaction since it is endothermic.
By adding more heat, equilibrium will shift to use up the extra heat, creating more NO2.
1. Concentration
2. Pressure and Volume
3. Temperature
Le Châtelier’s Principle states that if a system in equilibrium is subject to an external stress, the equilibrium will shift to minimize the effects of that stress.
Essentially, if equilibrium is disrupted, the system will do what it takes to get back to equilibrium
These factors come from last unit: factors that affect reaction rates
We are missing:
Nature of reactants
We can not change the nature of the reactants
Catalyst
Is not a stress that shifts the equilibrium because it increases the rate of both the forward and the reverse reactions
Review of Unit 1 concepts:
Is this a endothermic or exothermic process?
How would you incorporate the heat into the equation?