Equilibrium Flashcards
Reversible reactions
Reactions which can go both ways, ie the reactants can make products and products can make reactants
How are reversible reactions represented?
With a double arrow, half an arrow head on each one
What is dynamic equilibrium?
When the forward and backward reactions occur at the same rate
So concentration of reactants and products remain the same
Important aspects of equilibrium
Can only occur in closed systems
The reactions are still occurring, the rate at which reactants/products are made is equal so no visible change appeared
How is dynamic equilibrium achieved?
Reactants react in forward reaction and get used up (slows down) more product formed
Backwards reaction speeds up to form more products as a result
So eventually these reactions at same rate
Le Chateliers principle
When a system under dynamic equilibrium is changed, the position of equilibrium shifts to counteract the change
What factors can be changed to shift the position of equilibrium?
Concentration of either reactant or product
Temperature
Pressure (gases only)
Why does imposing changes on a system cause the position of equilibrium to shift?
Imposing a change would effect the dynamic equilibrium so the system changes the position of equilibrium to counteract the change eg lowering temp, lowering pressure or concentration
Endothermic and exothermic reversible reactions
One direction will be endothermic and the other direction is exothermic
When given a value of an energy change in a reaction, what is important?
The energy change value is for the foreword reaction
Endothermic energy values
Positive number (energy taken in)
Exothermic energy values
Negative number (energy released)
Increasing the temperature of a system means you give… to the system?
Heat is given to system
Effect of increasing temperature on dynamic equilibrium?
The equilibrium shifts to the endothermic direction so energy is taken in to counteract the increase in heat energy
What happens to the yield when you increase the temperature of a system?
You increase the yield of the products of the endothermic reaction
Decreasing the temperatures takes away… of a system in dynamic equilibrium?
Heat
Effect of decreasing temperature on dynamic equilibrium?
The equilibrium shifts to the exothermic reaction because heat was taken away so more heat released to counteract the heat that had been taken away
What happens to the yield when you decrease the temperature of a system?
You increase the products of the exothermic reaction
Increase in pressure does what to a system?
Decrease the volumes so there are more gas molecules in a given volume
Decrease in pressure does what to a system?
Increases the volume so there are less gas molecules in a given volume
What do changes in pressure refer to?
Only when all products/reactants are gases
What happens when you increase the pressure of gaseous chemicals in equilibrium
The equilibrium shifts to the side with fewer gaseous molecules to counteract the change and produce a higher concentration of the side with less molecules as shown by stoichiometry
What happens when you decrease the pressure of gaseous chemicals in equilibrium?
Equilibrium shifts to the side with more gaseous molecules to counteract the decrease by producing more reactants which have more gas molecules
According to stoichiometry
What happens if you increase the concentration of a reactant
The position of equilibrium shifts of the opposite direction (make more of the other reactant which was increased)
What happens if you decrease the concentration of a reactant?
The position of equilibrium shifts to the opposite direction (which makes more reactant) to oppose the decrease in concentration and form more reactants
How do catalysts effect a reversible reaction in dynamic equilibrium?
Increases the rate of both the forward and backward reaction
No effect on the yield because the catalyst increases the rate of BOTH reactions
What does position of equilibrium tells us?
The composition of the reaction mixture due to which reaction is favoured
Do catalysts have any effect on position of equilibrium?
No, they increase the rate of reaction equally on both sides so the rate changes on both sides (increases speed to achieve equilibrium) thus the position of equilibrium does not change
Why do we use catalysts in industrial processes?
So we can increases the rate of reaction while having a low temperature thus lower energy costs
Why do we use catalysts in industrial processes?
So we can increases the rate of reaction while having a low temperature thus lower energy costs
Industry: using high temperatures problem
High energy costs
Industry: high pressures problem
High cost to keep pumps which maintain the high pressure of gaseous molecules
What is one way to improve yield of reversible reactions in industry?
Recycle the reactants back
