equilibrium constant Kp Flashcards
what is Kp used for
to find equilibrium constant based on partial
pressures at a particular temp
what is the Kp expression
partial pressure of products/ partial pressure of reactants
NO SQUARE BRACKETS
what values do you use for the equation
ones given in question - no need to convert - can either be tonnes or grams
what are the units of Kp
- either Pa or kPa - just use what is in the question
- cancel out the Pa or kPa just like in kc
to convert from Kpa to Pa - x1000
what must all reactants and products be in
gas phase - as it is for an homogenous system
how to find partial pressure of each molecule
ICE
then find total mol at eq
divide mol of each /total mol
then x by total pressure
what term is used to describe the partial pressure dependent on the no. of moles present in a mixture
mole fraction
example
calculate partial pressure of these gases at eq
2 mol of A , 2 mol B and 3 mol C total pressure is 2 kPa
total mol = 2+2+3 = 7
pA = 2/7 x 2 = 0.57 kPa
pB = 2/7 x 2 = 0.57 kPa
pC = 3/7 x 2 = 0.86 kPa
then sub into Kp and work out eq
does the value of Kp change when add a catalyst
no
does the value of Kp change when change conc/ pressure/ vol
no
does the value of Kp change when change temp
yes
increase - Kp decreases if forward is exo
deacrease - Kp increase if forward is exo
what is partial pressure proportional to
no. of moles
what to remember to include in Kp expression
p in front of the moelcules