1.10 The Equilibrium Constant

Question 1

What is partial pressure ?

Answer 1

Each gas’ contribution to the total pressure

Question 2

How do you calculate partial pressure of a gas ?

Answer 2

Partial pressure p = mole fraction x total pressure

Question 3

What is a mole fraction ?

Answer 3

Mole fraction = moles of X / total moles in mixture

Question 4

A reaction is represented by aA(g) + bB(g) ⇌ cC(g) + dD(g), what is Kp for the system ?

Answer 4

*Kp = (pCᶜ x pDᵈ) /( pAᵃ x pBᵇ)
*pA = partial pressure of A
*ᵃ = moles of A.

Question 5

How do you calculate units for Kp ?

Answer 5

-Write out the units for partial pressure in the same arrangement as the Kp equation and cancel them out / multiply them
-Usually in Pa, kPa or atm : do not change the 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 pressure on Kp in this reaction ? :
Kp = (pCᶜ x pDᵈ) /( pAᵃ x pBᵇ)

Answer 7

Pressure does not affect Kp as moles of gas are the same on both sides

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 increase results in many more particles having energy greater than Ea -> more successful collisions
*Pressure - more particles in the same volume -> more successful collisions per second.