Equilibrium Flashcards
Reversible
Term for chemical equations that can undergo a reaction shift
Reaction shift
A reaction goes the other way
ie synthesis becomes decomposition
Dynamic equilibrium
The condition in which the rate of the forward reaction equals the rate of the forward reaction equals the rate of the reverse reaction,
But not the concentrations of the products and reactants
Equilibrium Constant (k)
Quantifies the concentrations of reactants and products in a reaction
Law of Mass Action
K=(product of individual product concentrations)/(product of individual reactant concentrations)
Coefficients in chemical equations becomes the exponent
Evaluation of the equilibrium constant
K»1 forward reaction is more common
Equilibrium constants in reversals
Invert the constant in reversals
Equilibrium constant when the chemical equation is multiplied
Multiply the constant by that same factor
Equilibrium constant for the elementary step in a reaction mechanism
Multiply the constants together
Partial pressure (Kp)
Equilibrium pressure of the reaction
Kp=Kc*(RT)^Δn
Δn- |molesProducts-molesReactants|
T- given in Kelvin
Will be expected to calculate all these variables given the others… Need practice
Reaction quotient (Q)
Concentrations of the products raised to their stoichiometric coefficients divided by the concentrations of the reactants raised to their stoichiometric coeffients… AT A CERTAIN POINT IN THE REACTION (Kc only applies at equilibrium)
Kc
Standard equilibrium constant
Concentrations of products to their coeffients over reactants to their coeffiecients
Concentrations of di-atomic molecules
The sub-2 in O2 remains in the conentration-variable box like [O2] and is not raised to a power when calculating Kc
Solid and liquid concentrations in Kc
Do not factor in at all when calculating for Kc
Only use the gasses in the reaction,
Their concentrations remain constant regardless of the amount of substance
Reaction progress towards equilibrium (%)
Q/Kc x100%
If >100%, reaction moves backwards towards reactants
Relationships between Q and Kc
If QKc, the reaction moves left (towards reactants)
Q=Kc reaction is at equilibrium at that point
Graphs of Q
Measure the product reactant concentration ratio over a change in (M)
Independent variable runs from 1M-0M for reactants and 0M-1M for products
Usually exponential, Kc represents one horizontal line on that graph, equilibrium when the two meet,
Reactions always move towards that point
Law of equlibrium
The natural tendency is towards a concentration of equilibrium
Q will always approach Kc from either direction
(Reverse if greater, forwards if less than)
Initial→final relationships
Provide Q with the initial values
Assume that they work towards Kc
Find Kc value (often given) and solve algebraically
Le chatelier’s principal
Any disturbance at equilibrium (temperature, volume, mass) and the rest of the system will work to restore equilibrium
(Causes either a forwards or reverse reaction)
Causing a forwards reaction
Add concentration to the reactants
Decrease concentration of the products
Increase concentration of the reactants
Increase volume (if products have fewer gas particles)
Decrease volume (if reactants have fewer gas particles)
Increasing temperature (if endothermic)
Decreasing temperature (if exothermic)
Causing a reverse reaction
Increase concentration of the products
Decrease concentration of the reactants
Increase volume (if reactants have fewer gas particles)
Decrease volume (if products have fewer gas particles)
Increasing temperature (if exothermic)
Decreasing temperature (if endothermic)
Increasing volume on a system at equilibrium
Shifts reaction in the direction of fewest gas particles
Increasing temperature on a system at equilibrium
Shifts the reaction in the more exothermic direction
Product quantity from Kc
Convert units of reactants to M
Use algebra to solve for product concentration given Kc
Convert [product]M to grams
Equilibrium constant (Kc) from Kp and temperature
Kc=Kp/(RT)^Δn
Δn- |molesProducts-molesReactants|
T- given in Kelvin
Will be expected to calculate all these variables given the others… Need practice
Units of Kp and converting
Always given as Pascals (Pa)
1 Pa=1N/m^2
=1/101,325 atm
=760/101,325 mmHg
=760/101,325 torr
=14.7/101,325 psi
Converting to K
C=(F-32)/1.8
K=C+273.15
Equilibrium constant from Gibbs Free Engergy
Ln(K)=ΔG/(-R*T)
Equilibrium constant (k) from standardcell potential
log(K)=E.cell/(0.0592/n
Calculating concentration from ‘k’ and time
K=Δ[material]/Δt
