Edexcel A Level Chemistry: 11: Equilibrim II
This flashcard set explains the equilibrium constant (Kc), how it's calculated, and its dependence on temperature. It also distinguishes between homogeneous and heterogeneous equilibria and clarifies why solids and pure liquids are excluded from Kc expressions.
What is Kc?
The equilibrium constant
Key Terms
What is Kc?
The equilibrium constant
What is kc calculated from?
The ratio of product concentration to reactant concentration
What is Kc a constant for?
A given temperature
What is a homogeneous equilibrium?
One where all the reactants and products are in the same state
What is a heterogeneous equilibrium?
One where the products and reactants aren’t all in the same state
Why are solids and pure liquids not included in Kc expressions?
Because their concentrations stay the same throughout the reaction
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| Term | Definition |
|---|---|
What is Kc? | The equilibrium constant |
What is kc calculated from? | The ratio of product concentration to reactant concentration |
What is Kc a constant for? |
|
What is a homogeneous equilibrium? | One where all the reactants and products are in the same state |
What is a heterogeneous equilibrium? | One where the products and reactants aren’t all in the same state |
Why are solids and pure liquids not included in Kc expressions? | Because their concentrations stay the same throughout the reaction |
How would you calculate a value for Kc? | Put the concentrations into the expression and calculate using them |
What can Kc be used to find? | Concentrations in an equilibrium mixture |
What can Kc be calculated from? | Experimental data |
What is the total pressure of a gas mixture equal to? | The sum of all the partial pressures of the gases |
What can partial pressure be worked out from? | Mole fractions |
What is a mole fraction? | The proportion of a gas mixture that is of a particular gas |
How is the mole fraction calculated? | No. Of moles of gas/total no. Of moles of gas |
How is partial pressure calculated? | Mole fraction of gas x total pressure |
What is Kp? | An equilibrium constant that is used when dealing wth gases |
How is Kp calculated? | From partial pressures of the gases |
What can Kp be used to find? | Partial pressures |
What does Kp for heterogeneous equilibrium include? | Only the gases |
What happens to equilibrium if the conditions change? | The position of it moves |
What factors affect equilibrium? | Concentration, pressure and temperature |
If the temperature increases, where does equilibrium move to? | The endothermic side of the reaction |
If pressure increases, where does equilibrium move to? | The side with fewer moles of gas |
What does the size of the equilibrium constant tell you? | Where the equilibrium lies |
The greater the Kc/Kp… | …the further to the right the equilibrium lies |
The small the value of Kc/Kp… | …the further tot he left the equilibrium lies |
What does the equilibrium constant for a reaction rely on? | The temperature of the reaction |
What happens in a reaction if concentrations change? | The concentrations of other reactants/products change in order to keep Kc the same |
How do concentration/pressure affect Kc/Kp? | The have no effect |
How do catalysts affect the position of equilibrium? | They have no effect |
Why do concentration and pressure not affect Kc/Kp? | Because although the amounts of products/reactants change, the ratio of reactants to products stays the same |