# **Chapter 7.1: Recognizing Equilibrium**

* **Equilibrium: products and reactants are occurring simultaneously at the same rate. water in a closed jar has the number of evaporating molecules and number of condensing molecules equal**
* Chemical processes that reach equilibrium:
  * **Homogeneous equilibrium:** the equilibrium reactions in which the reactants and products are in the same phase
  * **Heterogeneous equilibrium:** the equilibrium of reactions in which the reactants and products are in different phases

# **Chapter 7.2: Thermodynamics and Equilibrium**

* Favorable change: change that has a natural tendency to happen under certain conditions
* Enthalpy: Exothermic: when products have less enthalpy than reactants, it releases energy
* Endothermic: when reaction absorbs energy 
* Temperature: changes with the direction
* Entropy S: a tendency towards randomness or disorder in a system
* The second law of thermodynamics: total entropy of the universe is constantly increasing must add together changes in the entropy of the system, ∆*S*sys, and changes in the entropy of the surroundings, ∆*S*sur
* **Free energy:** available energy; useful work obtained from reaction
  * Also called *gibbs free energy G*
* ∆*G* = ∆*H* − *T*∆*S*
  * Change in free energy
  * Change in enthalpy
  * Change in entropy kelvin temperature
* ∆*G*
  * *Negative: forward reaction is favorable*
  * *Zero: reaction at equilibrium*
  * *Positive: reaction favorable in reverse direction only*

# **Chapter 7.3 The equilibrium constant**

* **Law of chemical equilibrium**: *At equilibrium, there is a constant ratio between the concentrations of the products and reactants in any change*
* **equilibrium constant *k*eq or kc**: forward rate constant divided by the reverse rate constant
  * kf / kr = *k*eq
  * kc: uses concentrated values when concentration is at equilibrium
* **ICE table:** table is used to record the initial, change, and equilibrium values of the reacting species,
* *K > 1, products are favoured. The equilibrium lies far to the right. Reactions where K is greater than 1010 are usually regarded as going to completion*
* *K ≈ 1, there are approximately equal concentrations of reactants and products at equilibrium*
* *K < 1, reactants are favoured. The equilibrium lies far to the left. Reactions in which K is smaller than 10−10 are usually regarded as not taking place at all*

# **7.4 Predicting the Direction of a Reaction**

* **Reaction quotient, *Q*c: expression that is identical to equilibrium constant expression, but concentration not necessarily at equilibrium**
* *Q*c = ( \[R\]*c*\[S\]*d ) / (* \[P\]*a*\[Q\]b )
  * If *Q*c equal to kc then it is *Q*c close to equilibrium
* **Le Châtelier’s principle:** *a dynamic equilibrium tends to respond so as to relieve the effect of any change in the conditions that affect the equilibrium*
  * **Common ion effect:** common ion involves adding ion to a solution in which theion is already present, the equilibrium shifts away from the added ion
    * applies Le Châtelier’s principle to ions in an aqueous solution
  * *Endothermic change* (∆*H* > 0):
    * An increase in temperature shifts the equilibrium to the right, forming more products.
      * *K*c increases.
    * A decrease in temperature shifts the equilibrium to the left, forming more reactants.
      * *K*c decreases.
  * *Exothermic change* (∆*H* < 0):
    * An increase in temperature shifts the equilibrium to the left, forming more reactants.
      * *K*c decreases.
    * A decrease in temperature shifts the equilibrium to the right, forming more products.
      * *K*c increases.
  * *Reducing the volume of an equilibrium mixture of gas (constant temperature), causes sift a shift in equilibrium in direction with few gas molecules*
  * Catalyst does not affect the position of equilibrium, only affects the time

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Chemistry

# **Chapter 7.1: Recognizing Equilibrium**

* **Equilibrium: products and reactants are occurring simultaneously at the same rate. water in a closed jar has the number of evaporating molecules and number of condensing molecules equal**
* Chemical processes that reach equilibrium:
  * **Homogeneous e

Chapter 7 - Reversible Reactions and Chemical Equilibrium

Bryce Spann

View the note Chapter 7 - Reversible Reactions and Chemical Equilibrium: Chapter 7.1: Recognizing EquilibriumEquilibrium: products and reactants are occurring simultaneously at the same rate. water in a closed jar has the number of evaporating molecules and number of condensing molecules equalChemic...