3.1.10 Equilibrium Constant Kp For Homogenous Systems

Question 1

What is kp?

Answer 1

Kp is an equilibrium constant based on partial pressures.

It tells you the ratio of products to reactants in a reaction at equilibrium.

Question 2

How do we write the kp expression?

Answer 2

In the reaction:

aA + bB ⇌ cC + dD

Kp = p(C)^c p(D)^d | products
÷ | ÷
. p(A)^a p(B)^b | reactants

(A) = concentration of A in moldm^-3
a = number of moles of A
p = partial pressure

( ) instead of [ ] (will be penalised)

Question 3

What do partial pressures add up to?

Answer 3

They add up to the total pressure.

Question 4

What should the mole fractions add up to in an equilibrium?

Answer 4

They should add up to 1.

Question 5

How do you calculate the mole fraction?

Answer 5

Mole fraction = moles of the desired gas
÷
total number of moles

Question 6

How do you calculate the partial pressure of a desired gas?

Answer 6

Partial pressure = mole fraction of desired gas x total pressure