Physical 10: Equilibrium Constant (Kp) Flashcards
What is Kp?
Pressure constant
How do you calculate Kp?
1) Balance the equation
2) Calculate equilibrium moles using ICE
3) Calculate mole fractions (equilibrium moles divided by total moles)
4) Work out partial pressures (mole fraction x total pressure)
5) Substitute partial pressures into Kp equation
6) Calculate units
How would you write the Kp expression?
*No square brackets
Otherwise works the same as equilibrium constant for concentrations
What is Le Chatelier’s Principle?
When a change is made to an equilibrium, the position of the equilibrium will shift to reestablish equilibrium
What is the only factor that affects pressure constant?
Temperature
What happens to Kp if you increase the temperature of a system in equilibrium?
The equilibrium will shift in the endothermic direction
Causing the partial pressure of the compounds in that direction to increase
Explain why Kp increases when temperature increases when the forward reaction is endothermic.
When temperature increases, the position of equilibrium shifts in the endothermic direction, so shifts to the forward direction
So more products produced, and the partial pressures of the products increase
So Kp becomes larger (numerator is greater than denominator)
What effect would a change in pressure have on equilibrium?
Increase in pressure, equilibrium would shift to the side of the equation with fewer molecules to reduce the pressure
Increasing the yield of that side of the equation
Only applies when there is a difference in number of molecules on either side of the equation
What effect do catalysts have on equilibrium?
Catalysts allow equilibrium to be reached more quickly, as they provide an alternative pathway with a lower activation energy, so that there are more particles with the activation energy, so the frequency of successful collisions increases
However catalysts don’t affect position of equilibrium or equilibrium constant
