Equilibria Flashcards
What are the conditions for equilibrium?
closed system
concentrations of the reactants and products are constant
What is a dynamic equilibrium?
The forward and backward reactions are occurring simultaneously at a constant rate.
State Le Chatelier’s principle
If a factor affecting the position of equilibrium is altered, the position of equilibrium will shift to oppose the change.
What happens in a reversible reaction at equilibrium?
the forward and reverse reactions proceed at equal rates
the concentrations of reactants and products remain constant
Which are the three factors that affect equilibrium?
Pressure
Temperature
Concentration
What is a homogeneous equilibrium?
A reaction where every species is in the same physical state
What would be the effect of increasing the concentration of a reactant on the equilibrium?
The equilibrium will shift to the right to oppose the change
Therefore, more products will be produced
What woulld be the effect of increasing the concentration of a product on the equilibrium?
The equilibrium will shift to the left to oppose the change
Therefore, the reverse reaction will go faster
What would be the effect of increasing pressure on the equilibrium?
The equilibrium will shift to the side with fewer gas molecules
Therefore, reducing pressure
What is only affected by the change in pressure?
Gases
What would be the effect of increasing temperature on the equilibrium?
The equilibrium will shift in the endothermic direction
Therefore, the temperature will be decreased
What would be the effect of decreasing temperature ont the equilibrium?
The equilibrium will shift in the exothermic direction
Therefore, the temperature will be increased?
What does NOT affect the equilibrium position?
Catalysts
Why do catalysts not affect the position of equilibrium and yield?
They allow equilibrium to be reached faster
They speed up both forward and backward reactions at the same rate, therefore having no effect on the yield
Why are catalysts used in industry?
They allow lower temperatures to be used as they provide alternative routes with lower activation energie
Therefore, there are lower energy costs
What is the Haber process?
The manufacturing of ammonia
N2(g) + 3H2(g) ↔ 2NH3(g)
What are the conditions for the Haber Process?
400-450 C
200-1000 atm
Iron catalyst
Why are compromised conditions used in industry?
Low temperatures produce very high yields but the reactions are slow
High pressures also produce high yields but the equipment required is very expensive
What is the Contact Process?
Stage 1: S(s) + O2(g) → SO2(g)
Stage 2: SO2(g) + 0.5O2(g) ↔ SO3(g)
What are the conditions for the Contact Process?
450C
1/2 atm
V2O5 catalyst
What are the conditions for the hydration of ethene to produce ethanol?
300C
70atm
conc. H3PO4
What is the equation for the hydration of ethene?
C2H4(g) + H2O(g) ↔ C2H5OH(g)
What do manufacturers do to improve the overall yields of processes?
They recycle uncreated reactants back into the reactors
When calculating Kc, how is concentration of a species represented?
[ ] = equilibrium concentration
How is Kc calculated?
Kc= [products] / [reactants]
What are the units for concentration?
mol dm^-3
How does temperature affect the Kc value?
When the temperature is altered, the Kc value and position of equilibrium will change
How does pressure affect the Kc value?
The position of equilibrium will change but the Kc value remains constant
How does a catalyst affect the Kc value?
A catalyst has no effect on the Kc value or the position of equilibrium
What happens when Kc< 1?
Equilibrium shifts to the left
What happens when Kc = 1?
Neither side of the system is favoured
What happens when Kc> 1?
Equilibrium shifts to the right
What is a homogeneous equilibrium?
Every species involved in the reaction is in the same phase
What is a heterogeneous equilibrium?
There are different phases in the equilibrium mixture
What is a phase?
A state of matter
Give an example of a homogenous equilibrium
The Contact Process
Give an example of a heterogeneous equilibrium?
The Haber Process
Why are solids and liquids not included in the Kc expression in a heterogeneous equilibrium?
Liquids and solids are incompressible
Therefore, their concentrations are constant
