Chapter 15 - Chemical Equilibrium Flashcards
Define chemical equilibrium.
when a reaction and its reverse reaction proceed at the same rate
As a system approaches equilibrium, _______________ are occurring.
both the forward and reverse reactions
At equilibrium, the forward and reverse reactions are proceeding _____________.
at the same rate
Once equilibrium is achieved, the amount of each reactant and product _______________.
remains constant
What does ⇌ denote in a reaction equation?
that it is an equilibrium reation
Define K eq.
the expression for the equilibrium constant
Define the Haber Process.
the industrial preparation of ammonia
Define K c.
an equilibrium constant in terms of molar concentration
Define K p.
an equilibrium constant in terms of partial pressure
What is the equilibrium expression for the generalized reaction a A + b B ⇌ d D + e E.
K c = [D]^d[E]^e / [A]^a[B]^b
What do [D]^d[E]^e denote in the equilibrium expression K c = [D]^d[E]^e / [A]^a[B]^b ?
the products
What do [A]^a[B]^b denote in the equilibrium expression K c = [D]^d[E]^e / [A]^a[B]^b?
the reactants
How can equilibrium be expressed in terms of partial pressure?
K p = (P D)^d(P E)^e / (P A)^a(P B)^b
What does the expression K p = K c (RT)^ Δn indicate?
(equilibrium constant in terms of partial pressure) = (equilibrium constant in terms of molar concentration) [(ideal gas constant)(absolute temperature of the gas)] ^ [(moles of gaseous product)-(moles of gaseous reactant)]
What is indicated if K»_space; 1?
the reaction favors products; products predominate at equilibrium
What is indicated if K «_space;1?
the reaction favors reactants; reactants predominate at equilibrium
The equilibrium constant of a reaction in the reverse reaction is the (same/reciprocal) of the equilibrium constant of the foreward reaction.
reciprocal
To find the new equilibrium constant of a reaction when equation has been multiplied by a number, _________.
raise the original equilibrium constant to that power
When two consecutive equilibria occur, the equations can be ______________.
added to give a single equilibrium
The equilibrium constant of the equation derived by adding two consecutive equilibrium equations is the ________ of two constants.
product
Define homogeneous equilibria.
occurs when all reactants and products are in the same phase
Define heterogeneous equilibria.
occurs when something in the equilibria is in a different phase
The value used for the concentration of a pure substance is always ____.
1
How are equilibrium concentrations deduced?
- Tabulate all known initial and equilibrium concentrations.
- For anything for which initial and equilibrium concentrations are known, calculate the change.
- Use the balanced equation to find change for all other reactants and products.
- Use initial concentrations and changes to find equilibrium concentration of all species.
- Calculate the equilibrium constant using the equilibrium concentrations.
Define LeChâtelier’s Principle.
“If a system at equilibrium is disturbed by a change in temperature, pressure, or the concentration of one of the components, the system will shift its equilibrium position so as to counteract the effect of the disturbance.”
If the system is in equilibrium, adding a reaction component ______________.
will result in some of it being used up
If the system is in equilibrium, removing a reaction component ____________.
will result in some of it being produced
When gases are involved in equilibrium, a change in ___________ will affect equilibrium.
pressure or volume
Higher ______ or lower _______ favors the side of the equation with more moles.
volume, pressure
How does heat affect an endothermic reaction in equilibrium?
it acts like a reactant, driving the reaction to favor products
How does heat affect an exothermic reaction in equilibrium?
it acts like a product, driving the reaction to favor reactants
What is the one instance in which a system in equilibrium can be affected by a catalyst?
the Haber Process
Why can the equilibrium of the Haber Process be affected by a catalyst?
the activation energy required for the reaction is quite high
How do catalysts affect the forward and reverse reactions of a system?
they increase the rate of both the forward and reverse reactions
In the presence of a catalyst, _________ is achieved faster, but the ___________ remains unaltered.
equilibrium, composition
In the presence of a catalyst, ___________ is lowered, allowing ___________ to be established at a lower temperature.
activation energy, equilibrium
