Equilibria Flashcards
What type of reaction reaches an dynamic equilibrium state?
All reversible reactions
Name two features of dynamic equilibrium?
Forward and backwards reactions occur at the same rate
Concentration of reactants and products stay constant
What do we use position of equilibrium for?
To describe the composition of the equilibrium mixture
What happens if the position of equilibrium favoured reactants?
The equilibrium mixture would be mostly reactants
What does Le Chatelier’s principle state?
If an external condition is changed the equilibrium will shift to try to oppose the change (and try to reverse it).
What is Le Chatelier’s principle used for?
To work out how changing external conditions such as temperature and pressure affect the position of equilibrium.
What will the equilibrium do if the temperature is increased?
The equilibrium will shift to try to oppose this and move to oppose this and move in the endothermic direction to try and reduce the temperature by absorbing heat
What will the equilibrium do if the temperature is decreased?
The equilibrium will try to oppose this and move in an endothermic direction to try and increase the temperature given out heat.
What might low temperatures do to the yield?
Low temperatures may give a higher yield of product but may also result in slow rates of reaction. Often a compromise temperature is used that gives a reasonable yield and rate.
What will increasing the pressure do to the equilibrium position?
It will shift the equilibrium towards the side that has fewer moles of gas to oppose the change and thereby reduce the pressure
What will decreasing the pressure do to the equilibrium position?
Shift the equilibrium towards the side with more moles of gas to oppose the pressure and thereby increase the pressure
What happens if the number of gas is equal on both sides of the equation if the pressure is changed?
Nothing
What does the term dynamic mean?
Both forwards and backwards reactions are occurring simultaneously
What would increasing the pressure do to the yield of product?
It would increase it and give a faster rate
What would increasing the pressure do to cost?
Increase them
Industrially high pressures are expensive to produce and the equipment to contain the high pressure is expensive
Why are Industrially high pressures are expensive to produce?
High electrical costs for pumping gases to make high pressure
What goes increasing OH- ions do to the equilibrium?
Shifts them to oppose this and move in a forward direction to remove and decrease the concentration of OH ions
It will shift to the reverse reaction giving higher yield
What does adding H+ do to solution?
Reduces the concentration so the equilibrium shift back to the forward reaction giving brown colour.
Explain effect of catalyst on equilibrium?
No effect on rate of equilibrium but will speed up rate of which equilibrium is achieved
Why doesn’t a catalyst affect the equilibrium?
It speeds the forwards and backwards reactions by the same amount
Habour process equation?
N2(g) + 3H2(g) 2NH3(g) + 92.4 kJ
Conditions used for habour process?
450oC
200-1000 atmospheric pressures
Iron catalyst
Why isn’t a lower temperature used for habour process?
Gives good yield but slow rate
Compromise condition
Why isn’t a higher pressure used?
Gives good yield and high rate but expensive to maintain pressure (building+ electricity pumping)
Enthalpy change for habour process?
- negative
Exothermic
