Equilibrium and Acid Base 1 Flashcards
what is the definition of equilibrium?
no observable changes in macroscopic properties (example: colour, concentration, temperature)
what is phase equilibrium?
a single chemical substance existing in more than one phase in a closed system.
ex: a mix of ice and water at 0°C
what is solubility equilibrium?
a single chemical solute interacting with a solvent substance, where excess solute is in contact with the saturated solution
ex: solid in the bottom of a saturated solution
what is chemical reaction equilibrium?
several substances: the reactants and products of a chemical reaction
ex: dissociation of weak acids or bases in water
Reactions are often __________ which means that not only are the products formed but the reactants can be formed
reversible
- we use a double arrow to show this relationship
What two states can equilibrium be
static or dynamic
static equilibrium meaning
no changes occuring at any level
dynamic equilibrium meaning
the change one way is countered by an equal and opposite change the other way
the rates for a forward and reverse reaction will proceed at different rates. They depend on what?
The concentration of the reactants and products
- the forward direction will initially be the fastest if we only have reactants A and B
- As the products C and D are formed, the reverse reaction will speed up and the forward reaction will slow down.
- At some point the rates of forward and reverse reaction become equal.
a system is said to be in a state of dynamic equilibrium when?
- The rates of the forward and reverse reactions are equal
- The observable (macroscopic) properties of the system such as temperature, pressure, concentration, pH are constant
- the system is closed at a constant pressure
- The reaction must be reversible
In a chemical equalibrium, the rate of the forward reaction is _____ to the rate of the reverse reaction!
equal
what are the three classes of chemical equilibria?
- reactants favoured (percent rxn < 50%)
- products favoured (percent rxn > 50%)
- quantitative to the right (percent rxn > 99%)
what is the law of equilibrium
there is a constant ratio between the concentrations of the products and the concentrations of the reactants at the equilibrium
at a given temperature for a given reaction, an equilibrium constant (K꜀) will always be the same no matter what the initial concentrations of the species. This is useful because it allows us to predict the amount of a substance made even when we do not get a complete reaction
K꜀ is constant for a reaction at a given ___________. If you change the temperature, K꜀ also changes
temperature
When determining K꜀ use only the species that are in ___ or _______ states unless all states are the ____ then use them all
gas
aqueous
same
the higher the value of K꜀, the greater the tendency for the reaction to favor the ________________
forward reaction (the products)
If K꜀ is greater than 1, then the reaction is _________ favoured
products
If K꜀ is less than 1, then the reaction is _________ favoured
reactants
K꜀ indicates the ________________ and not the rate of reaction
Percent reaction
catalysts will not affect the [] at equilibrium… _____________________________
they only increase the rate of rxn (by lowering activation energy)
what is the three-step process of Le Chatelier’s principle?
- initial equilibrium state
- shifting non-equilibrium state
- new equilibrium state
what does le chatelier’s principle state?
When a chemical system at equilibrium is disturbed by a change in property of the system, the system adjusts in a way that opposes the change
a system can be affected by a change in concentration, temperature, and/or volume (pressure)
In a concentration change of a system, what happens if the concentration increases vs decreases
An increase in the concentration of the products or reactants favours the other side of the equation
A decrease in the concentration of the products or reactants favours the same side of the equation
ex: N₂(g) + 3 H₂(g) ⇌ 2 NH₃(g)
↑ [N₂(g)] will shift the equilibrium to the products/to the right
↑ [NH₃(g)] will shift the equilibrium to the reactants
↓ [NH₃(g)] will shift the equilibrium to the products
in a temperature change of a system, how is Kc affected by the transfer of temperature?
energy is treated like a reactant or product
a change in temperature is the only stress that will change the value of Kc!!
if the shift is toward the product side, Kc will increase
if the shift is towards the reactant side, Kc will decrease
ex:
reactants + energy ⇌ products
reactants ⇌ products + energy
- if cooled, equilibrium shifts so more heat is produced
- if heated, equilibrium shifts away from the heat so it cools down
In volume and pressure changes of a system, with gases, volume and pressure are related (volume ____, pressure __)
down, up
In volume and pressure changes of a system, the concentration of a gas is related to volume (volume ____, Concentration __)
down, up
In volume and pressure changes of a system, an increase in concentration caused by a drop in volume causes a shift toward the side of the equation with _____ moles of gas
fewer
Example: N2(g) + 3 H2(g) ⇌ 2 NH3(g)
will shift to NH3(g)
In volume and pressure changes of a system, if the number of moles are the same on both sides of the reaction, a change in volume has _________
no effect
In volume and pressure changes of a system, changes in volume and pressure have _________ of value of Kc
no effect
what does ICE stand for?
I = initial concentrations
C = change in concentrations
E = equilibrium concentrations
what do we use to calculate equilibrium/initial concentrations of reactants or products?
Kc and ice tables
what is the formula for percent reaction?
(equilibrium yield/maximum yield)*100
what is the only stress that will change the value of kc?
a change in temperature
Draw the graph for Dynamic Equilibrium
Draw a graph to demonstrate the changes to equilibrium for the equation: N₂(g) + 3H₂(g) ⇌ 2NH₃(g) + energy for the following stresses:
a) Addition of H₂(g) c) Decrease in volume
b) the Addition of inert gas, the addition of catalyst d) an Increase in energy
