Edexcel A Level Chemistry: 10: Equilibrium I
These flashcards cover the concept of dynamic equilibrium in reversible reactions, explaining how and when it is achieved, and emphasizing the importance of a closed system for maintaining equilibrium.
What can reversible reactions reach?
Dynamic euqillibrium
Key Terms
What can reversible reactions reach?
Dynamic euqillibrium
As the reactants are used up, what happens to the forward reaction?
It slows down
When is dynamic equilibrium achieved?
When the forwards reaction is going at exactly the same rate as the backwards reaction and the amounts of reactants and products aren’t changing
What does dynamic equilibrium happen in?
A closed system
What is Kc?
The equilibrium constant
What does Kc give you an idea of?
How far to the left or right the equilibrium is
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| Term | Definition |
|---|---|
What can reversible reactions reach? | Dynamic euqillibrium |
As the reactants are used up, what happens to the forward reaction? | It slows down |
When is dynamic equilibrium achieved? | When the forwards reaction is going at exactly the same rate as the backwards reaction and the amounts of reactants and products aren’t changing |
What does dynamic equilibrium happen in? | A closed system |
What is Kc? | The equilibrium constant |
What does Kc give you an idea of? | How far to the left or right the equilibrium is |
| A system in which everything is in the same physical state |
What can Kc be worked out using? | The concentrations of reactants and products at equilibrium |
Which reactants and products are included in Kc for homogeneous equilibria? | All of them |
What is the equation for Kc? | [products]/[reactants] |
What is a heterogeneous equilibria? | One in which not everything is in the same physical state |
What is not included in the Kc expression for heterogeneous equilibria? | Pure liquids or solids |
Why are solids not included in the Kc expression? | Because their concentration is constant |
Why are pure liquids not included in the Kc expression? | Because their concentration is constant |
Why aren’t catalysts included in the Kc expressions? | Because they don’t affect the equilibrium concentrations of the products or reactants |
How do catalysts affect equilibrium? | They increase the rate at which equilibrium is reached |
What is Le Chatelier’s principle? | If there is a change in concentration, pressure or temperature, the equilibrium will move to help counteract the change |
If the position of equilibrium is altered, what will happen? | The amounts of products and reactants at equlibrium change |
What happens if the concentration of a reactant is increased? | The equilibrium shifts to the right to use up the extra reactants |
What happens if the concentration of a product is increased? | Equilibrium shifts to the left to remove the extra product |
What happens if the pressure is increased? | The equilibrium shifts to the side with fewer moles, reducing the pressure |
What does pressure affect? | Gases |
What happens if pressure is decreased? | Equilibrium shifts to the side with the most moles to raise the pressure |
What happens if temprature is increased? | The equilibrium shifts to the endothermic side to absorb the heat |
What happens if temperature is decreased? | The equilibrium shifts to the exothermic side to replace the heat |
What happens if the forward reaction is endothermic? | The reverse reaction is exothermic |
How are conditions chosen in industry? | As a compromise |
What are conditions chosen to produce? | A high rate and high yield |
How is ethanol made? | From ethene and steam |
What is the equation for ethanol production? | C2H4 + H2O --> C2H5OH |
What pressure is used for ethanol production? | 60-70 atm |
What temperature is used for ethanol production? | 300 degrees |
What catalyst is used for ethanol production? | Phosphoric acid |
Why is the temperature for ethanol production relatively low? | Because the forward reaction is exothermic, so lower temperatures favour it |