Equilibria Flashcards
What is Le - Chateliers principle
A system in equilibrium will respond to oppose any change imposed upon it
Describe the relationship between concentration and rate in a reversible reaction at equilibrium
-Forward and reverse reactions proceed at equal rates
-Concentration of reactants & products remain constant
When the equilibrium lies to the left, are there more reactants or products?
More reactants
When the equilibrium lies to the right, are there more products or reactants
More products
What are the 3 factors that affect equilibrium position
Temperature
Pressure
Concentration
What is the equation showing equilibria and forming ethanol
C2H4 + H2O <–> C2H5OH
What is the equation showing equilibria and forming methanol
CO + 2H2 <—> CH3OH
What are the conditions for forming ethanol in equilibria
T - 300 C
P - 6.5MPa
Catalyst - H3PO3
What are the conditions for forming methanol in equilibria
T - 400 C
P - 5.0 MPa
Catalyst - Cr2O3 + ZnO
What is the equation for Kc from this
aA + bB <—> cC + dD
[C]^c [D]^d / [A]^a [B]^b
What is the equation for Kc
Concentration of products/ Concentration of reactants
How do we calculate units of Kc
Each square bracket is equal to 1moldm-3, and they cancel each other out. When there are the same number of brackets on numerator and denominator, there are no units
How does temperature affect Kc for an endothermic reaction
An increase in temperature increases Kc for an endothermic reaction
Explain how temperature affects Kc for an endothermic reaction
-An increase in temperature for an endothermic reaction shifts the equilibrium to the right
- Meaning conc of products increase and conc of reactants decreases, therefore Kc increases
Which side does increase temperature favour
Increasing temperature favours the endothermic direction
Which side does increasing pressure favour
The side with fewer moles
How does temperature affect Kc for an exothermic reaction
Increase in temperature means Kc decreases for an exothermic reaction
Explain how temperature affects Kc for an exothermic reaction
- Increase in temperature for an exothermic reaction means equilibrium shifts to the left
- This means concentration of products decrease and concentration of reactants increases meaning a decrease in Kc value
How does concentration affect equilibrium position
If concentration of reactants increases, equilibrium will shift right
If concentration of products increases, equilibrium will shift left
If concentrations of both products and reactants decrease equally, equilibrium moves to side with more moles to oppose decrease in conc
What are the conditions for the Haber process
450 C
200atm
Iron catalyst
What is a closed system
Nothing can leave or enter
What are the features of a system in a state of dynamic equilibrium
- Conc of reactants and products remain constant
- Forward rate = backwards rate
- Closed system
How does a catalyst affect the position of an equilibrium
Doesn’t affect equilibrium position as forward and backwards reaction increase at the same rate
How does a decrease in overall concentration affect equilibrium position
Equilibrium moves to side with more miles to oppose decreases in conc
