Equilibrium constant Kp

Question 1

What is partial pressure

Answer 1

Each gas’s contribution to the total pressure

Question 2

How would you calculate the partial pressure of a gas

Answer 2

Partial pressure p = mole fraction x total pressure

Question 3

What is the mole fraction

Answer 3

Mole fraction of gas X = number of moles of gas X in the mixture / total number of moles of gas in the mixture

Question 4

A reaction is represented by Aa (g) + bB (g) ⇋ cC (g) + dD (g)

Answer 4

For the reaction: aA + bB ⇋ cC + dD
Kp = (pC^c pD^d) / (pA^a pB^b)
Where pA = partial pressure of A and a = number of moles of A

Question 5

How do you calculate the units for Kp

Answer 5

Write out the units for the partial pressures in the same arrangement as the Kp equation and cancel out / multiply together
Usually in Pa, kPa, atm etc
DO NOT CHANGE UNITS

Question 6

What is the effect of increasing temperature on Kp for an endothermic reaction

Answer 6

Equilibrium shifts to the right so partial pressure of products increase so Kp increases

Question 7

What is the effect of increasing the overall pressure on Kp for this reaction

Answer 7

Pressure does not affect Kp as, if moles of are not the same on each side, either top or bottom of Kp expression will have a total pressure term that does not cancel

Question 8

What would be the kinetic effect of increasing the temperature and pressure for any reaction

Answer 8

Increasing both will increase the rate of reaction as:
Temperature - many more particles have energy greater than or equal to activation energy —> more successful collisions per second
Pressure - more particles in the same volume —> more successful collisions per seconf