Equilibrium I Flashcards
(21 cards)
Give five features of a reaction at dynamic equilibrium
1) reaction is reversible
2) reaction is in a closed system (no reactants/products added/removed)
3) forward and reverse reaction are continuously occurring
4) rate of forwards reaction = rate of backwards reaction
5) concentrations remain constant (not necessarily equal)
Give three factors that affect the position of equilibrium
1) temperature
2) pressure
3) concentration
Why do catalysts not have an effect on the position of equilibrium
they speed up both the forward and the reverse reaction equally
What is a homogenous system
all reactants and products are in the same phase
What is a heterogenous system
at least two different phases are present in the reaction
What is the reaction quotient (Q)
the mathematical relationship between concentrations of components in a reaction
When does the reaction quotient apply
at any time in the reaction
What is the equilibrium constant (Kc)
the mathematical relationship between concentrations of components in a reaction at equilibrium
When does the equilibrium constant apply
only applies at equilibrium
What components of the reaction should be included when calculating Kc in a homogenous reaction
include everything in equation
What components of the reaction should be included when calculating Kc in a heterogenous reaction
only gases and aqueous solutions
(they can change concentration by solids and pure liquids can’t)
What does Kc < 1 x 10^-7 mean for the reaction
the reaction is not happening
What does Kc < 1 mean for the reaction
equilibrium lies to the left
- more reactants are made
What does Kc = 1 mean for the reaction
equilibrium lies in the middle
What does Kc > 1 mean for the reaction
equilibrium lies to the right
- more products are made
What does Kc > 1 x 10^7 mean for the reaction
the reaction is at completion
Describe how to calculate equilibrium concentrations in a reaction
calculate equilibrium moles using the balanced equation to find the changes in moles
divide equilibrium moles by the volume to find concentration
What happens to Kc if temperature is increased (H=-ve)
if temperature is increased we favour the reverse (endothermic) reaction
the denominator of Kc will increase
so Kc will decrease and the position of equilibrium will shift left
What happens to Kc if concentration of a reactant is increased
if concentration is changed the system is no longer in equilibrium
Kc doesn’t change
if we increase the concentration of a reactant, the denominator of Q will increase (reaction quotient)
equilibrium will shift right to restore Q to equal Kc
What effect does increasing the pressure have on the equilibrium
an increase in pressure will cause the equilibrium to shift to the side with the fewest molecules
What effect does decreasing the pressure have on the equilibrium
a decrease in pressure will cause the equilibrium to shift to the side with the most molecules
