Equilibria Flashcards
What is an Equilibrium mixture?
Where the proportions of all components in a mixture remain constant
Dynamic equilibrium
Where the forwards and backwards reaction occur at the same rate
Conditions for equilibrium
Can only be reached in a closed system
What is Le chatelier’s principle
If a system at equilibrium is disturbed, the equilibrium moves in the direction to reduce the disturbance
Changing concentration in equilibrium
Increasing the concentration of REACTANTS or decreasing concentration of PRODUCTS causes a shift to the RIGHT (forward)
Increasing concentration of the PRODUCTS or decreasing concentration of REACTANTS causes a shift to the LEFT (Backwards)
Changing pressure in equilibrium
Only affect gaseous equilibria
Increasing the pressure of the system will cause equilibrium to shift to the position with less moles
Decreasing the pressure of the system will cause equilibrium to shift to the position with more moles
If number of moles is equal, pressure changes have no effect
Changing temperature on equilibrium
Increasing temperature of a system will cause a shift to the endothermic direction
decreasing temperature will cause a shift to the exothermic direction
Catalyst effect on equilibrium
Have no effect on equilibria position as it increases the rate of the forwards and backwards reaction equally
however do allow equilibrium to be reached quicker
What is Kc and formula for
2A + B <–> 2C
Equilibrium constant
Kc = [C]^2/[A]^2[B]
Where C A and B are concentrations
(mol dm^3)
Effect of temperature on Kc value
If reaction is endothermic, increasing temp increases Kc
If reaction exothermic, increasing temp decreases Kc
Effect of concentration on Kc
Change in concentration has no effect on Kc
Equilibrium will shift to oppose changes, keeping Kc constant
What does the size of Kc tell us
If greater than 1, products predominate over reactants, equilibrium position over the right
If less than 1, reactants predominate over products, equilibrium position over the left
Effect of catalyst on Kc
No effect on Kc value as catalyst affect both forwards and backwards reaction equally
What constant does gaseous equilibria use
Kp
Partial pressure calculation
Mole fraction X total pressure
