3.1.10 Equilibrium Constant Kp For Homogenous Systems

Question 1

Total pressure

Answer 1

The total pressure of a gas mixture is the sum of all the partial pressures of the individual gases
- in a mixture if gases , each gas contributes to the total pressure

Question 2

Partial pressure

Answer 2

The partial pressure is the pressure a gas would exert it it occupied a container on its own

Question 3

To work out partial pressure what do you need to do

Answer 3

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

Second -
Partial pressure of gas = mole fraction of a gas x total pressure of the mixture

Question 4

Kp eq

Answer 4

Kp = products / reactants

The equilibrium constant Kp is deduced from the equation for a reversible reaction occurring in the gas phase . It is calculated from partial pressure for a system at constant temperature.

Question 5

Effect of temperature on Kp

Answer 5

Kp is affected by temp as changing temp means eq shifts to reactants / products side to counteract the change so then it increase the pressure of reactants / products.

Kp is larger is equilibrium lies to the right
-> more reactants , Kp decreases ( large denominator)
-> more products , Kp increases ( large numerator)

Kp must be calculated for a system at CONSTANT TEMPERATURE

Question 6

Increase / decrease in temp exothermic rxn

Answer 6

Increase = decrease KP as eq shifts to left in endo direction so pressure of reactants increases
Decrease = increases Kp as eq shifts right in exo direction so pressure of products increases

Question 7

Increase / decrease in temp endothermic rxn

Answer 7

Increase = increase in Kp as eq shifts to right in endo direction so pressure of products increases
Decrease = decrease in Kp as eq shifts in exo direction so pressure of reactants increases

Question 8

Is Kp affected by pressure changes

Answer 8

Kp IS NOT AFFECTED BY PRESSURE CHANGES
- this is because changing the pressure of reactants makes the equilibrium shift in the other direction to increase the pressure of the other side , so number of particles doesn’t change.
- changing the total pressure only affects the equilibrium position when there is a change in the total number of molecules on either side of the rxn

Question 9

Is Kp affected by catalysts

Answer 9

Kp IS NKT AFFECTED BY CATALYSTS
- this is bc using a catalyst only speeds up the rate of reaction . They don’t affect the number of particles
- however , increasing the pressure , temp + using catalyst on a gas phase rxn will INCREASE the rate at which equilibrium is reached as there will be more collisions between molecules