3.1.6- Equilibria Flashcards
Define dynamic equilibria
Both forward and backward reaction occurring at same time
4 features of dynamic equilibrium
- Both reactant and products are present at all time
- The equilibria can be approached from either side
- Reaction is dynamic moving backward and forward
- concentration of reactants and products remain constant
What is homogenous
Reactant and products are in the same phase
What heterogeneous
Reactants and products are in different phases
What is le Chanteliers principle
When a change is applied to a system in dynamic equilibria, the system reacts in such a way as to oppose the effect of the change
What happens if the concentration is changed in a reversible reaction
- Kc will not be affected
- Equilibria will move opposite way to where it has been added
Example of changing concentration in a reversible reaction
A+2B = C +D
Add more A
The equilibria will move to the right to oppose the change
What happens when you change pressure in a reversible reaction
Increase - move to side with fewer gaseous molecules
Decrease - move to side more gaseous molecules
What happens when temperature is altered in a reversible reaction
Kc moves to produce a new constant
What happens when you increase the temperature of a reversible reaction
Exothermic moves to left
Endothermic moves to right
What happens when temperature is decreased in reversible reaction
Exothermic moves to right
Endothermic moves to left
If temperature is increased explanation in reversible reaction
Move in endothermic direction to absorb heat
If temperature is decreases explaination
Move in exothermic to give out heat to surroundings
How does a catalyst affect reversible reactions
Does not affect Kc
Reach equilibria quicker because catalyst increase the forward and backward reaction rates equally
What are two industrial processes with reversible reactions
The Haber process
The contact process
Explain temperate used in the haber process
450
I.e. A moderate temperature
Adv+ increases the rate of reaction and within working range of catalyst
Dis- lower yield because prefers lower temperature and energy costs
Explain pressure used in haber process
20 MPa
I.e. High pressure
Adv+ increase the rate and increases the yield. High pressure is favoured
Dis- energy costs and plant costs
Explain the use of catalyst in the haber process
Adv+ increases rate and lowers temperature to be used
Dis- cost and recovery and deactivation of catalyst
What are additional conditions of the haber process
Remove NH3 as it is formed
Cool mixture down NH3 forms first
Recycle unused gases
Uses of NH3
Fertiliser
Medicine
Explosives
What is the equation for the contact process
2SO2 + O2 = 2SO3
Explain temperature used in contact process
Moderate temperature
Adv+ increases rate of reaction and in range of catalyst
Dis - lowers yield as prefers lower temperature and energy costs
Explain pressure in the contact process
High pressure 200KPa
Adv+ increases the rate of reaction and increases yield high pressure is favoured
Dis- energy costs and plant costs
Explain catalyst used in contact process
V2O5 (vanadium pentoxide)
Adv+ increases rate and lower temperature needed
Dis - Catalysts are expensive
Show how to calculate Kc from this equation
aA+bB = cC+dD
[A]a[B]b
What is Kc not affected by
A change in concentration
A change in pressure
Adding a catalyst
What is Kc changed by
A change in temperature
