3.1.10 Equilibrium constant Kp

What is the total pressure in a reaction?

The sum of all the pressures of the individual gases

What is partial pressure?

The contribution a single gas makes towards the total pressure of a system

What is the equation to calculate the mole fraction of a gas?

Mole fraction of a gas = number of moles of gas / total number of moles of gas in mixture

What is the equation to calculate partial pressure?

Partial pressure = mole fraction of gas x total pressure in mixture

What does ICE stand for in the ICE table?

• I: initial moles

• C: change in moles

• E: moles at equilibrium

What is the difference between Kp & Kc?

Kp is the equilibrium constant for an equilibrium reaction involving gases, so partial pressures are used instead of concentrations

Write a Kp expression for this reaction

What are the units for Kp?

kPa

What is the only factor that has an effect on the value of Kp?

Temperature

Why is Kp only valid at one specific temperature?

Changing the temperature shifts the position of equilibrium & alters the equilibrium partial pressures, so the value of Kp changes

How does temperature affect the value of Kp?

• If temperature change causes equilibrium to shift right, Kp will increase

• If temperature change causes equilibrium to shift left, Kp will decrease

How does pressure affect the vale of Kp?

No effect

How do catalysts affect the value of Kp?

Has no effect on the value of Kp → only speeds up the rate of the forward & reverse reaction (rate at which equilibrium is reached)

How to convert from:

• kPa to Pa

• Pa to MPa

• kPa to Pa: multiply by 10³

• Pa to MPa: multiply by 10⁶

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