Equilibrium Flashcards
Open System
Matter can also be exchanged with the surroundings
Closed system
No matter (only energy) is exchanged with the surroundings
Examples of reversible processes (3)
Evaporation and condensation of water in a sealed bottle
Dissolving and crystallisation taking place in a saturated solution
Reaction between ethanoic acid and water in a sealed bottle of vinegar
When does a closed chemical system reach a state of chemical equilibrium?
When the rate of the forward reaction is equal to the rate of the opposite reaction.
What occurs in a system at chemical equilibrium? (2)
The amounts of the reactant and product species remain constant and so its observable properties (temperature, pressure, colour etc) of the system are also constant.
Reaction continues but there is no net reaction since the rate of the forward reaction is equal to the rate of the reverse reaction
What occurs in a system at chemical equilibrium? (Observable properties)
The amounts of the reactant and product species remain constant and so its observable properties (temperature, pressure, colour etc) of the system are also constant.
What occurs in a system at chemical equilibrium? (net reaction)
Reaction continues but there is no net reaction since the rate of the forward reaction is equal to the rate of the reverse reaction
Do open systems reach a state of equilibrium
No
Equilibrium constant (Kc)
The relationship between the equilibrium concentrations of the reactant s and products at a particular temperature has a constant value
What is the general reaction for the equilibrium constant? aA + bB ⇄cC + dD
Kc = [C]ⁿ [D]ⁿ / [A]ⁿ [B]ⁿ
State the Le Chatelier’s Principle
If a system at equilibrium is subjected to a change in conditions, the system will adjust to re-establish equilibrium in such a way as to partially counteract the imposed change.
What are the 4 additions that can change a system that is already at equilibrium?
Change in concentration
Change in Temperature
Change in Volume/Pressure of a Gaseous system
Addition of a Catalyst
What occurs to a system at equilibrium when concentration of reactants is increased?
The forward reaction will speed up to use up some of the extra reactants. The reverse reaction rate then also increases and eventually catches up until both rates are equal again.
Therefore, some of the extra reactants will have been used up, and the concentration of products will be more than before.
What occurs to a system at equilibrium when the concentration of the products is increased?
The reverse reaction will speed up to use up some of the extra products will have been used up, and the concentration of reactants will be more than before
What occurs to a system at equilibrium when temperature changes? (increased)
If the temperature is increased, net reaction will proceed in the direction that absorbs heat (endothermic direction).
What occurs to a system at equilibrium when temperature changes? (decreased)
If temperature is decreased, net reaction occurs in the direction that releases heat (exothermic)
What occurs to a system at equilibrium when volume/pressure of a gaseous system changes?
The volume of a gas is indirectly proportional to the pressure it exerts.
What occurs to a system at equilibrium when volume/pressure of a gaseous system changes? (volume increases)
Increasing the volume of a gaseous system at equilibrium, results in a decrease in pressure, net reaction proceeds in the direction that produces the greatest number of particles.
What occurs to a system at equilibrium when volume/pressure of a gaseous system changes? (pressure)
If pressure is increased, volume decreases, net reaction occurs in the direction that produces the least number of particles.
What occurs to a system at equilibrium when a catalyst is added? (already at equilibrium)
Adding a catalyst to a system that is already at chemical equilibrium will have no effect on the system.
What occurs to a system at equilibrium when a catalyst is added? (not at equilibrium)
A catalyst added to a system NOT at equilibrium will speed up the rate at which equilibrium is established
Position of equilibrium
The relative amounts of reactants and products at equilibrium
What are the 3 conditions that the position of equilibrium may be changed by, for any equilibrium system?
Adding or removing a reactant or product
Changing the pressure by changing the volume (for equilibria involving gases)
Diluting (for equilibria in solution)
Changing the temperature
Total Pressure =
Total Pressure=Sum of the partial pressures of all gases in the mixture