EQUILIBRIA Flashcards
Define dynamic
Both forward and backward reactions are occurring simultaneously
Outline the two features of dynamic equilibirum
- Forward and backward reactions are occurring at equal rates
- The concentrations of reactants and products stays constant
Outline Le Chatelier’s PRinciple
If an external condition is changed the equilibrium will shift to oppose the change
Describe the effects of increasing the temperature on equilibrium in an exothermic reaction
The equilibrium shifts to the products
To decrease the temperature
And oppose the shift
Giving a lower product yield
Describe the effects of decreasing the temperature on equilibrium in an endothermic reaction
The equilibrium shifts to the products
To decrease the temperature
And oppose the shift
Giving a lower product yield
Describe the effects of increasing the temperature on equilibrium in an endothermic reaction
The equilibrium shifts to the the reactants
To decrease the temperature
And oppose the shift
Giving a higher product yield
Describe the effects of decreasing the temperature on equilibrium in an exothermic reaction
The equilibrium shifts to the the reactants
To decrease the temperature
And oppose the shift
Giving a higher product yield
Why is a compromise temperature used
Lower temperatures give a higher yield
But slow the rate of reaction
Compromise temperatures give a reasonable rate and yield
Describe the effects of decreasing the pressure on equilibrium
The equilibrium shifts to the side with more moles of gas
To increase the pressure
And oppose the shift
Giving a lower yield on the side with fewer moles
Describe the effects of increasing the pressure on equilibrium
The equilibrium shifts to the side with more moles of gas
To increase the pressure
And oppose the shift
Giving a higher yield on the side with fewer moles
Describe the effects of changing pressure on equilibrium when moles is equal either side
No effect on position of equilibrium
Why is an increased pressure not often used to give a higher yield?
Expensive to produce (elctric for pumping to give high pressure)
Expensive equipment
Outweigh the higher yield and faster rate
Describe the effects of increasing the concentration of the reactants on equilibrium
The equilibrium shifts to the the reactants
To decrease the concentration
And oppose the shift
Giving a higher product yield
Describe the effects of increasing the concentration of the products on equilibrium
The equilibrium shifts to the the products
To decrease the concentration
And oppose the shift
Giving a lower product yield
Describe the effects of decreasing the concentration of the products on equilibrium
The equilibrium shifts to the the reactants
To increase the concentration
And oppose the shift
Giving a higher product yield
Describe the effects of decreasing the concentration of the reactants on equilibrium
The equilibrium shifts to the the products
To increase the concentration
And oppose the shift
Giving a lower product yield
Outline the effects of a catalyst on equilibirium
No effect on position of equilibrium
Speeds up the rate at which equilibrium is achieved
Speeds up the rate of the forward and backward reaction equally
Outline the Haber Process
N2 + 3H2 = 2NH3 (exo)
450C, 200-1000atm, iron catalyst
Outline the Contact Process
1) S(s) + O2(g) > SO2(g)
2) SO2(g) + 0.5O2(g) = SO3(g) (exo)
450C, 10atm, V2O5 catalyst
Outline the production of methanol from CO
CO(g) +2H2)g) = CH3OH (exo)
400C, 50atm, chromium and zinc oxide catalysts
Outline the hydration of ethene to produce ethanol
C2H4(g) + H2O(g) = CH3CH2OH(l) (exo)
300C, 70atm, Concentrated H3PO4 catalyst
Where mA + nB = pC + qD
write the formula for Kc
Kc = ([C]^p x [D]^q) / ([A]^m x [B]^n
Moles of reactant @ equilibrium =
Moles of product @ equilibrium =
initial moles - moles reacted
initial moles + moles formed
What does Kc show?
Larger Kc values = greater amount of product
Small Kc values = equilibrium favours reactants
What condition affects Kc?
Temperature
Outline the steps to a method for calculating an equilibrium constant (Kc)
- Prepare an equilibrium mixture
- Titrate the equilibrium mixture
- Work out the initial moles of reactants
- Work out the equilibrium moles of acid (from the titre results)
- Calculate the equilibrium amount of moles from other substances
- Calculate the equilibrium constant (Kc)
