What does a large number of Kc mean
further the position of equilibrium towards the products
What are the two types of equilibria
- homogenous
- heterogenous
What is homogenous equilibrium
- contains equilibrium species that all have the same state or phase
What is heterogenou equilibrium
- contains equilibrium specie that have different states or phases
What does homogenous equilbia Kc expression contain
concentrations of all species
What does the Kc expression of heterogenous equilibria contain and why
- gases and aqueous only
- as solids and liquids are essentially constant
What are the steps for figuring out Kc
- work out equilibrium moles of all species
- find equilibrium conctentrations
- write expression for Kc and substitute vsalues
Describe the method to determine Kc
- in a concical flask mix together 0.1mol of CH3COOH and o.1mol C2H5OH add 0.05 mol of HCL as an acid catalyst to the flask
- the total volume of mixture in the flask is 20cm3
- the amount of water in the aqueous acid catalyst is 0.5 mol
- add 0.05 mol of HCL (aq) to a second conicall flask as a control
- stopper both flasks and leave for a week to reach equilibrium
- carry oit a titration on the equilibrium mixture using a standard solution of sodium hydroxidew
- repeat the titration with the control to determine the amount of acid catlayst been acid
How are equilibrira involving gases expressed
in terms of Kp
What does Kp stand for
eqilibriu constant in terms of partial pressures
Decribe the relationship between concentration and pressure
proportional to one another
What is the mole fraction of a gas
is the same as its proportion by volume to the total volume of gases in a gas mixture
What is the formula for mole fraction
- number of mols/total number of moles in gas mixture
What is partial pressure
- contribution that the gas make towards the total pressure p
- sum of partila pressures of each gas equals total pressure
What is the formula for partial pressure
- mole fraction x total pressure
What are the three rules for the equilibrium position
- if concentration of a species increases equilibrium position shifts in the direction that reduces the concentration
- if the pressure is increaed the equilibrium poition shifts towards the side with fewer gasous moles
- i the temperature is increased the equillibrium position shifts in the endothermic direction
What does K=1 indicate
an equilibrium halfway between reactants and products
What does K=100 indicate
an equilibrium well in favour of products
What does K=0.01 indicate
equilibrium well in favour of reactants
What does the value of K express
the exact position of equilibrium
What happens to k at a set temperature
k is constant and does not change despite any modifications to concentration, pressure or the prescence of a catalyst
Describe what happens to K af the temperature is changed
k does change
a temperature change is the only condition that will cause k to change it value
What happens to equilibrium if the forward reaction is exothermic
- the equilibrium constant decreases with increasing temperature
- raising the temperature decreases the equilibrium yield of products
Describe what hapens if the forward reaction is endothermic
- the equilibriumm constant increases with increasing temperature
- raising the temperature increases equilibriu m yield of products
