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Unit 15 - Chemical Equilibrium - Coggle Diagram
Unit 15 - Chemical Equilibrium
15.1 - 15.3 The Concept of Equilibrium and Equilibrium Constant
The concentrations of reactants and products no longer change with time.
Neither reactants nor products can escape from the system (closed system)
A particular ratio of concentration (or pressure) terms remains a constant
aA + bB ⇋ cC + dD
The Practical Meaning of K
If K >> 1 The reaction is product favored
If K << 1 The reaction is reactant favored
Manipulating Equilibrium Constants
If the reactants and products are reversed, Kc and KP will be the reciprocal.
The equilibrium constant of a reaction that has been multiplied by a number is the equilibrium constant raised to a power that is equal to that number.
Equilibrium Mechanisms with Multiple Steps
Once the equations have been combined, mathematically the overall KC will be the product of the individual equilibrium constants.
15.4 - 15.5 Heterogeneous Equilibria and Calculating Equilibrium Constants
When all substances at equilibrium are in the same phase, we call it homogeneous equilibrium.
When there are different states of matter involving substances at equilibrium, we call it heterogeneous equilibrium.
Therefore, whenever a pure solid (s) or pure liquid (l) is involved in a heterogeneous equilibrium equation, its concentration [ ] is NOT included in the Kc
ICE Charts
Initial
Change
Equilibrium
15.6 Applications of Equilibrium Constants
In other words, Q gives the same ratio as Kc but for a system that is not at equilibrium
Q to K
If Q = K, the system is at equilibrium.
If Q > K, there is too much product, and the equilibrium shifts to the left.
If Q < K, there is too much reactant, and the equilibrium shifts to the right.
15.7 Le Châtelier’s Principle
Le Châtelier’s Principle - If a system at equilibrium is disturbed by a change in temperature, pressure, or the concentration of one of the components, the system will shift its equilibrium position so as to counteract the effect of the disturbance.
3 types of disturbances:
Adding or removing a reactant or product
Changing the pressure by changing the volume
Changing the temperature
Effects of Change in Pressure and Volume
If the volume of a system is decreased, the pressure of the gases will increase.
When this disturbance occurs, the equilibrium will shift to the side of the reaction that has less moles of a gas
If the volume of a system is increased, the pressure of the gases will decrease.
When this disturbance occurs, the equilibrium will shift to the side of the reaction that has more moles of a gas
Effect of Temperature Changes
changing the temperature will both shift the equilibrium and change the Kc value.
Endothermic: Reactants + heat ⇋ Products (heat acts as a reactant) 𝚫H > 0
(Also, increasing temperature results in an increase in K for endothermic reactions.)
Exothermic: Reactants ⇋ Products + heat (heat acts as a product) 𝚫H < 0
(Also, increasing temperature results in a decrease in K for exothermic reactions.)
The Effect of Catalysts
While a catalyst increases the rate of a reaction, it has no effect on the composition of the equilibrium mixture.