CHEM EQUILL Flashcards
What is a reversible reaction
It refers to a reaction that can proceed in both the forward and backwards direction, is never complete and only attains dynamic equillibrium
What is a dynamic equillibrium
It refers to a reversible reaction that experiences no changes in concentrations of products or reactants
What are the characteristics of a dynamic equillibrium
(i) no net change in concentrations of products or reactants
(ii) can only be attained in a closed system
What types of dynamic equillibrium are there
(i) homogeneous
(ii) heterogeneous
What is a homogeneous equillibrium
It is an equillibrium that is reached when the reactants of products are in the same phase
What is a heterogeneous equillibrium
It is an equillibrium reached when the products and reactants are in different phases
What properties of the equillibrium constant are there
(i) it is mathematically determined by the equillibrium concentrations alone
(ii) it is dependant on the rate constants of forward and backward reactions - dependant on temperature
(iii) does not take into account concentrations of products or reactants that remain essentially the same in initial and equillibrium state
What exceptions of concentrations does it not take into account
(i) immiscible liquids
(ii) solids
(iii) water
What is the difference between Kp and Kc
Kp is in terms of equillibrium partial pressure while Kc is in terms of equillibrium concentrations
How do you find equillibrium constant if not all concentrations are given
Initial
Change
Equillibrum
table can be used as changes of concentrations are mathematically determined by stoichometric ratio of reaction
What is the significance of the value of equillibrium constant
(i) position of equillibrium (extent of reaction
(ii) value of change in Gibbs’ Free Energy
(iii) the equillibrium constant is independant of changes in initial concentrations or catalyst
What does it mean if equillibrium constant is large (change in G)wise
If equillibrium constant is large, it suggests that the forwards reaction is more spontaneous than the backwards reaction by a large extent. Hence the change in G is negative.
What does it mean if equillibrium constant is low (change in G)wise
It suggests that the forward reaction is less spontaneous than the backwards reaction. So the change in G is positive
What does it mean if the equillibrium constant is large (position of equillibrium)wise
It suggests that for dynamic equillibrium to be reached, a greater concentration of product is needed than reactants. So, the position of equillibrium lies more to the right
What does it mean if the equillibrium constant is small (position of equillibrium)wise
It suggests that for dynamic equillubrium to be attained, a larger concentration of reactants is needed. So the position of equillibrium lies more to the left
What does it mean if the equillibrium constant is directly proportional to the temperature
It suggests that the the enthalpy change is endothermic
What does it mean if the equillibrium constant is inversely proportional to temperature
It suggests that the forward reaction is exothermic
What is Le Chatelier’s principle
It states that when a system in equillibrium is disturbed, it will change its position of equillibrium to counteract the change imposed to re-establish equillibrium
What changes will cause the position of equillibrium to change
(i) change in concentration of reactants or products
(ii) change in partial pressure of reactants or products
(iii) change in total pressure
(iv) change in temperature
How does an increase in concentration of products induce a change in position of equillibrium
An increase in products will result in the backwards reaction being favoured to counteract the increase in concentration products. Thus position of equillibrium lies more to the left
How does an increase in total pressure change position of equillibrium
Dependant on stoichometric ratio - the system will favour the reaction that produces fewer gaseous molecules. Position of equillibrium shifts leftwards if backward reaction, opposite if forward
Do changes in pressure or concentration affect equillibrium constant
No.
How does an increase in temperature affect the system of a reversible reaction with a exothermic forward reaction
The system will favour the backward reaction to counteract the increase in temperature as it is endothermic. This shifts position of equillibrium leftwards while equillibrium constant decreases
Does increasing total pressure by inserting inert gas change position of equillibrium
No. Partial pressures of product and reactants remain the same, thus total pressure of system remains undisturbed
(System refering solely to product and reactants)
Will adding a catalyst change position of equillibrium
No. Both rate of reactions inconsiderate of directions increases by the same extent. However, progession towards dynamic equillibrium is faster
