Equilibrium Flashcards
equilibrium (2)
When the rate of the forward reaction equals the rate of the reverse reaction, the concentrations of the reactant and product species remain constant over time
What slows the slows the forward reaction rate?
The decreasing concentration of the reactant
what speeds the reverse reaction rate?
the increasing product concentration
Reaction Quotient
+how is it derived
Tells us if reaction is at equilibrium or not
the reaction quotient is derived directly from the stoichiometry of the balanced equation as
Reaction quotient when products and reactants are gases
a reaction quotient may be similarly derived using partial pressures:
as a reaction proceeds towards equilibrium what varies?
Explain how it does
The numerical value of Q varies
As the reaction proceeds toward equilibrium in the forward direction, reactant concentrations decrease (as does the denominator of Qc), product concentration increases (as does the numerator of Qc), and the reaction quotient consequently increases. When equilibrium is achieved, the concentrations of reactants and product remain constant, as does the value of Qc.
If the reaction begins with only product present……
Qc+what happens
the value of Qc is initially undefined (immeasurably large, or infinite):
In this case, the reaction proceeds toward equilibrium in the reverse direction. The product concentration and the numerator of Qc decrease with time, the reactant concentrations and the denominator of Qc increase, and the reaction quotient consequently decreases until it becomes constant at equilibrium.
equilibrium constant, K
The constant value of Q exhibited by a system at equilibrium
law of mass action
At a given temperature, the reaction quotient for a system at equilibrium is constant. aka Equilibrium constants are constant at constant temperature
A reaction exhibiting a large K indicates that it….
most of the reactant has been converted to product
a small K indicates the reaction achieves equilibrium after
very little reactant has been converted
A homogeneous equilibrium
all reactants and products (and any catalysts, if applicable) are present in the same phase.
Water and reaction quotient
Why? What only does it RQ include?
Water is not included in the reaction quotient because its conctration cannot be increased. It is already pure.
reaction quotients include concentration or pressure terms only for gaseous and solute species.
And so, the relationship between Kc and KP is
heterogeneous equilibrium
involves reactants and products in two or more different phases,
How to find Kp with Kc
kp=kc (RT)^n
n is the order so remember product-reactant stoich coefficient wise
so what does an equilibrium reaction not include? write me the reaction kc/kp for this question then:
pure liquids and solids
coupled equilibria
coupled equilibria involve two or more separate chemical reactions that share one or more reactants or products.
equilibrium constant for the reversed equation is
simply the reciprocal of that for the forward equation.
Changing the stoichiometric coefficients in an equation by some factor x results in
an exponential change in the equilibrium constant by that same factor:
Adding two or more equilibrium equations together yields
an overall equation whose equilibrium constant is the mathematical product of the individual reaction’s K values:
How to find overall reaction Kc when given the elementrary equations plus elementary kc? (3)
- see if the reverse elementary step Kc have to be reversed or not. depending if products/reactants of the overall equation are on which side
- see if you need to exponentially increase elemnetary Kc, (kc)^x based on elementary coefficients and overal equation coefficient
- multiply the modified elementary coefficient all tgt
If an equilibrium system is subjected to a change in conditions that affects these reaction rates (forward and reverse reactions taking place at equal rates) differently (a stress), then
talk about what the rate now is and what will happen
the rates are no longer equal and the system is not at equilibrium. The system will subsequently experience a net reaction in the direction of greater rate (a shift) that will re-establish the equilibrium.
Le Châtelier’s principle
if an equilibrium system is stressed, the system will experience a shift in response to the stress that re-establishes equilibrium.