Kp Flashcards
true or false -> Kp uses round not square brackets
true
Kp =
homogenous (same gas phase only)
only temperature changes Kp
not pressure (pressure only affects position of eq)
increase temp
If temperature is increased the reaction will shift to oppose the change
and move in the backwards endothermic direction. The position of
equilibrium shifts left. The value of Kp gets smaller as there are fewer
products.
pressure
The position of equilibrium will
change if pressure is altered but
the value of Kp stays constant
as Kp only varies with
temperature.
f pressure is increased the reaction will shift to oppose the change
and move in the forward direction to the side with fewer moles of gas.
The position of equilibrium shifts right. The value of Kp stays the
same though as only temperature changes the value of Kp
total pressure of mixture
mixture = A + B + C = ptotal = pA + pB + pC
calculate partial pressure
Partial pressure of A = (mole fraction of A) x total pressure
calculate mole fraction
Mole fraction of A = number of moles of A in equilibrium mixture / total moles of gas in equilibrium mixture
steps to calculating Kp
1) ICE table to find equilbrium moles
2) find mole fraction
3) find partial pressure
4) put into Kp expression
Kp units
Kp units = Pa so 1/pa = p^-1 or 2Pa/ 1 = Pa^2
Kp expression
Kp expression for H2 (g) + I2 (g) –> 2HI (g)
Kp = (p HI)2 / p(I2) p(H2)
definitions
Kp is the equilibrium constant calculated from partial pressures for a system at constant temperatures
–> partial pressure = the pressure that the gas would have if alone occupied the volume of the whole mixture
larger Kp
The larger the Kp the greater the amount of products. If Kp is small we say the equilibrium favours the reactants
CO (g) + 2H2 (g) –> CH3OH(g)
62.8 mol CO
146mol H2
Eq methanol = 26.2 mol
total pressure 9.50Mpa
Find Kp
0.023 mpa-2
calculate the total number of moles of gas present in the eq mixture
Cl2 at eq = 0.75 mol
SO2Cl2 = 1.00 at initial
SO2 = unknown
0.75 + 0.75 + 0.25 = 1.75
