Unit 2: Reaction Equilibrium Flashcards
In a reaction that is said to be “reversible” while the forward reaction proceeds so does….
The reverse reaction
In a closed system most reactions are _____.
Reversible
At equilibrium the forward reaction rate is always equal to the…
Reverse reaction rate
Only _____ reactions form an equilibrium
Reversible
For a reaction to be reversible a ___ ____ is needed
Closed system
At equilibrium no _____ changes occur
Macroscopic
At equilibrium the _____ of both the reactants and products are constant (but not necessarily equal).
Concentration
A dynamic equilibrium if upset will…
Re-establish itself
A state of equilibrium exists whenever… (4 things)
- There is a closed system
- The reaction is reversible
- There is no change in macroscopic properties
- The temperature is constant
Give 3 properties you could monitor so see if a equilibrium exists
- change in pressure
- change in concentration
- change in colour
The two driving factors for all chemical processes are…
- enthalpy
- entropy
Entropy is…
The tendency to achieve a higher state of disorder/randomness
Enthalpy is…
The tendency to achieve a lower heat content
All reactions want a ____ enthalpy and a ____ entropy
Lower
Higher
Rank the following states by which is most favoured by entropy to least favoured by entropy. (Include > symbols)
Solid, liquid, aqueous, and gas
Gas»aqueous>liquid» solid
Note that aqueous has more entropy than liquids but it is not as great of a difference between liquids and solids
When both entropy and enthalpy favour the formation of products a _____ does not exist
Equilibrium
When both entropy and enthalpy favours the reactants the ____ does not go to _____
Reaction
Completion
What 4 factors can shift the equilibrium
- concentration
- pressure
- temperature
- volume
According to Le Chatelier’s principle whenever a stress is added is applied to a system the system will ____ so as to ____ the stress and re-establish ____.
Shift
Reduce
Equilibrium
An increase in concentration increases the ____ ____ which in turn increases the ____ ____.
Collision frequency
Reaction rate
Equilibrium favours a shift ____ from the increased concentration.
Away
A decrease in volume of the closed system means there is a _____ ____ of the system which ____ the ____ ____ which leads to the ____ ____ increasing
Increased pressure
Increases
Collision frequency
Reaction rate
Equilibrium favours a shift ____ from the greater number of gas molecules to the _____ number of gas molecules
Away
Lower
An increase of the pressure of a container is a ____ in the volume of the container which leads to an ____ of the collision frequency and reaction rate
Decrease
Increase
Pressure can be increased by adding a ____ gas and this added gas will have ____ affect on the equilibrium
Noble
No
When a noble gas is added the overall ____ of each species of gas in the equilibrium will ____
Pressure
Increase
An _____ in temperature increases both the forward and reverse reaction rates
Increase
When the reaction is endothermic and heat is added the equilibrium shifts toward the ___ side
Product
When the reaction is ______ and heat is added the equilibrium shifts toward the reactant side
Exothermic
What effect do catalysts have on equilibrium
Catalysts have no effect on equilibrium
Catalysts increase both the forward and reverse reaction rate equally and equilibrium is reached faster
[products]/[reactants] is the ____ expression
Keq
When using the Keq expression make sure that the power (which are the coefficients of the products and reactants) are always in the ____ whole number ration
Lowest
If you reverse the chemical equation then the equilibrium expression will be the _____ of the original constant
Reciprocal
When Keq is large the _____are favoured
Products
Keq is small when the ____ are favoured
Reactants
In a closed system nothing can….
Leave or enter
Temperature ____ (can/cannot) effect the equilibrium
Can
At a new temperature _____ (the same/a new) equilibrium is attained
A new
Is the equilibrium different if the reaction started with and excess of products?
No
Same goes for excess of reactants
In a ____ equilibrium no macroscopic changes occur
Dynamic
When a dynamic equilibrium exists all observable qualities are constant but at the molecular level there is….
Constant back and forth reaction between reactants and products (which is a perfect balance)
The rate of consumption of reactants is equal to the rate of….
Production of reactants
Is [reactants] always equal to [products]?
No. The [reactants] differs from [products] in general but they can be equal
Are the [reactants] and [products] constant at equilibrium?
Yes
A system that is capable of equilibrium that is not at equilibrium will tend to…
Move toward a position of equilibrium
A _____ change is a change which occurs by itself, without outside assistance
Spontaneous
A reaction is expected to move spontaneously to the side of the reaction having minimum energy if…..
The energy barrier is low enough
Endothermic reactions are not expected to occur ___ without if sufficient heat is not available
Spontaneously
The side of the reaction having minimum _____ (entropy/enthalpy) is said to be favoured because molecules will tend to go to or remain at minimum energy
Enthalpy
Do all Exothermic reactions go to completion?
No. Sometime the reverse reaction occurs to some extent so the reaction is then at equilibrium
Can an endothermic reaction occur spontaneously? If so give an example
Yes. Chemical cold packs.
Why is a highly random state favoured over a highly ordered state?
Because there are more random states possible
What is entropy?
The amount of randomness in a system
The greater the difference in the amount of randomness of products vs reactants the greater the ____ drive of the system
Entropy
Minimum ____ favours the side of the reaction containing the “heat” term
Enthalpy
If there is only a single phase in the entire reaction entropy favours the side with….
The most molecules
Le Chatelier’s Principle is…
If a closed system at equilibrium is subjected to a change, processes will occur that tend to counteract that change
Solids and pure liquids are not included in the equilibrium expression because…
They have a constant concentration
What is the only change that can affect the value of keq
Temperature change
