Equilibrium Constant Kp

Question 1

What is partial pressure?

Answer 1

Pressure that the gas would have if only the gas occupied the volume of the whole mixture

Question 2

How do you calculate partial pressure of a gas?

Answer 2

Mole fraction of gas x partial pressure

Question 3

How do you calculate mole fraction?

Answer 3

1) Use ICE diagram to find moles of gas at equilibrium

2) Total moles = all moles of gas at equilibrium

3) Mole fraction = (mole of 1 gas at equilibrium) / (total moles of gas at equilibrium)

Question 4

Write the Kp expression for the following equation:
2SO2 (g) + O2 (g) <–> 2SO3 (g)

Answer 4

Kp = (pp SO3)^2 / (pp SO2)^2 x ppO2

Question 5

How would you work out the units for Kp in this equation:
2SO2 (g) + O2 (g) <–> 2SO3 (g)

Answer 5

1) (kPa^2) / kPa x kPa^2

2) 1 / kPa

3) kPa^-1

Question 6

What does a large Kp value suggest?

Answer 6

There is a large amount of products

Question 7

What does a small Kp value suggest?

Answer 7

Equilibrium favours reactants

Question 8

Which factors have an effect on Kp?

Answer 8

Temperature only

Question 9

How does temperature affect the position of equilibrium and Kp

Answer 9

Both will change

Question 10

How does Kp and equilibrium change with this equation if temperature is increased? (Forward reaction is exothermic)

N2 (g) + 3H2 (g) <–> 2NH3 (g)

Answer 10

1) Reaction shifts backward in the endothermic reaction to oppose the change

2) Equilibrium shifts to the left

3) Kp decreases as there are fewer products

Question 11

Effect of pressure and concentration on equilibrium position and Kp value

Answer 11

Shifts equilibrium

No effect on Kp