Equilibrium constant Kp
Why is the pressure of a gas measured instead of its concentration?
>Concentration + pressure of gas = directly proportional >In ideal gas equation, p = (n/V) * RT >RT is constant at constant temperature >And (n/V) also = concentration >Hence pressure is proportional to concentration
Describe the qualitative effects of changes in temperature on the value of Kp for an exothermic reaction
>If temperature increases, position of equilibrium shifts to left >Yield of product decreases: Kp = ↓p(B) / ↑p(A) Therefore, Kp decreases >If temperature decreases, position of equilibrium shifts to right >Yield of product increases: Kp = ↑p(B) / ↓p(A) Therefore, Kp increases
Describe the qualitative effects of changes in temperature on the value of Kp for an endothermic reaction
>If temperature increases, position of equilibrium shifts to right >Yield of product increases: Kp = ↑p(B) / ↓p(A) Therefore, Kp increases >If temperature decreases, position of equilibrium shifts to left >Yield of product decreases: Kp = ↓p(B) / ↑p(A) Therefore, Kp decreases
If pressure/concentration was increased, state the effect on the rate, rate constant, yield and equilibrium constant
>Increased rate of reaction >No change to either constant >Yield depends on stoichiometry
State how total pressure is calculated
>Sum of all partial pressures
What is the change in condition that will affect Kp?
>Temperature >Catalyst only results in system reaching equilibrium faster >Equilibrium is re-established when pressure changes, so changes in pressure have no effect
What is Kp?
Equilibrium constant calculated from partial pressures for a system at constant temperature
What is partial pressure?
PP of one of the gases in a mixture = pressure it would exert if it alone occupied the whole container
Describe how partial pressure is derived from mole fraction and total pressure
Pa = Xa * P >Pa is partial pressure of gas A >Xa is mole fraction of gas A >P is total pressure
What is the equilibrium constnat Kp deduced from?
The equation for a reversible reaction occuring in the gas phase
State the units of Kp
kPa