3.1.6 Equilibria Flashcards
All reversible reactions reach a _____/_____ state
All reversible reactions reach a dynamic equilibrium state
If the number of moles of gas is the same on both sides of a reversible reaction, pressure ____/_____/__/_____/__/___/_____/__/________
If the number of moles of gas is the same on both sides of a reversible reaction, pressure will have no effect on the position of equilibrium.
The _____ the Kc the _______ the amount of products
The larger the Kc the greater the amount of products
What is the only external condition that affects value of Kc?
Temperature
How does temperature affect the value of Kc?
-temperature will cause a shift in the position of equilibrium
-if eq. shifts to the right, Kc will increase as there are more products
-if eq. shifts to the left, Kc will decrease as there are less products
What does the term dynamic mean in dynamic equilibrium?
Both forward and backward reactions are occuring simultaenously
What are two features of dynamic equilibrium?
- Forward and backward reactions occuring at equal rates
- Concentrations of both reactants and products remain constant
What does Le Chatelier’s principle state?
If an external condition is changed, equilibrium will shift to oppose the change.
What is the effect of increasing temperature on equilibrium?
-equilibrium shifts in the endothermic direction
-tries to reduce temperature by absorbing heat
What is the effect of decreasing temperature on equilibrium?
-equilibrium shifts in the exothermic direction
-tries to increase temperature by giving out heat
(ESQ) What effect would increasing temperature have on the yield of Ammonia? (4)
ON GOOGLE DOC
-shifts in the endothermic direction
-backwards reaction is favoured to try and decrease temperature
-position of equilibrium shifts to the left
-lower yield of ammonia
What’s the issue surrounding equilibrium if the forward reaction is exothermic? How is this overcome?
-decreasing temperature would shift equilibrium to the right
-however; it would lower the rate of reaction (rate of attainment of equilibrium)
-a compromsie temperature is used that gives a reasonable yield and rate
What is the effect of increasing pressure on equilibrium?
-equilibrium shifts to the side with fewer moles
-to oppose the change and thereby reducing pressure
What is the effect of decreasing pressure on equilibrium?
-equilibrium shifts to the side with more moles
-to oppose the change and thereby increase pressure
(ESQ) What effect would increasing pressure have on the yield of methanol?
GOOGLE DOC!
-equilibrium shifts to oppose the increase in pressure, moving to the side with fewer gas molecules
-position of equilibrium shifts to the right because there are 3 moles on the left but only one on the right
-resulting in a higher yield of methanol
What are the drawbacks of using high pressures in industry?
-high electrical energy costs for pumping gases to maintain high pressure
-equipment is expensive
What is the effect of increasing concentration on equilibrium?
-equilibrium shifts to oppose this change
-moves in direction to remove and decrease the concentration of the substance added
What is the effect of decreasing concentration on equilibrium?
-equilibrium shifts to oppose this change
-moves in direction to remove and increase the concentration of the substance removed
What is the effect of catalysts on equilibrium?
-no effect on position of equilibrium
-speeds up the rate at which equilibrium is achieved
How do you work out the equilibrium constant?
GOOGLE DOC
GOOGLE DOC
How do you work out the unit of Kc?
Units will change depending on the equation that is formed. Write each individual unit and see what it cancels to.
Define the term ‘catalyst’ and explain how a catalyst works: MS [3]
A substance that speeds up the reaction, but is chemically unchanged at the end (not used up)
They work by providing an alternative reaction pathway
With lower activation energy
Give the meaning of the term activation energy: MS [2]
The activation energy is the minimum amount of energy
needed for a reaction to occur with successful collisions
With reference to a Maxwell–Boltzmann distribution, explain why an increase in temperature increases the rate of a chemical reaction: MS [4]
The peak of the curve will be displaced to the right
The peak will be lower than the original curve
Particles have more kinetic energy, hence more collisions occure
More particles have energies greater than or equal to Ea
State and explain the effect of an increase in total pressure on the rate of attainment of an equilibrium: MS [3]
Increased rate of equilibrium achievement
More particles will be present in a given space
More successful collisions will occur
Explain what must happen for a reaction to occur between molecules of two different gases: MS [2]
The molecules of the gases must collide
With at least the activation energy
Explain why a small increase in temperature has a large effect on the initial rate of a reaction: MS [1]
A small increase in temperature will cause many more molecules to have at least the activation energy
