1.10 Equilibrium Constant

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), what Kp for the system

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 pressures of products increase, so Kp increases

Question 7

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

Kp = pC^c pD^d
——————
pA^a pB^b

Answer 7

Kp = pC^c pD^d
——————
pA^a pB^b

Pressure does not affect Kp as , if moles of gas 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 will 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 the activation energy —> more successful collisions per second

Pressure-more particles in the same volume —> more successful collisions per second