A - Kp Flashcards
Explain what partial pressure means.
In a mixture of gases, each gas contributes to the total pressure. This contribution is called its partial pressure, p, and is the pressure the gas would exert if it occupied the container on its own.
The sum of the partial pressures of all the gases in a mixture is the total pressure.
What is the total pressure of a gas mixture, give the individual partial pressures?
The total pressure of a gas mixture is the sun of all the partial pressures of the individual gases.
What does px mean?
‘The partial pressure of X’
What is a mole fraction?
The proportion of a gas mixture that is made up of a particular gas.
How do you work out the mole fraction of a gas in a mixture?
Number of moles of gas (A)
———————————————————————
Total number of moles of gas in the mixture
How do you work out the partial pressure if a gas given it’s mole fraction?
Mole fraction of gas (A) X total pressure of the mixture
What is Kp?
The equilibrium constant, for a reversible reaction, calculated from the partial pressures for a system at constant temperature.
(Where all the reactants and products are gases).
How do you find the units for Kp?
Put the units for the partial pressures into the expression instead of the numbers, and cancel to find the final units.
According to Le Chatelier’s principle, what happens to the equilibrium of gas equilibria when you increase or decrease the pressure?
If you increase the pressure, the equilibrium shifts to the side with fewer moles of gas.
If you decrease the pressure, the equilibrium shifts to the side with more moles of gas.
According to Le Chatelier’s principle, what happens to a gas equilibria when you increase or decrease the temperature?
If you increase the temperature, the equilibrium shifts in the endothermic direction.
If you decrease the temperature, the equilibrium shifts in the exothermic direction.
A particular value of Kp is only valid for a given what?
Temperature.
Does Kp change if you change the pressure? Why or why not?
No, because the equilibrium shifts to oppose the change.
Does adding a catalyst affect the value of Kp?
No, it just increases the rate of attainment of equilibrium.
