5.1.2- How Far? Flashcards
What does it mean when a reaction is at equilibrium?
The rate of forwards and reverse reactions are equal
What are methods that can be used to measure equilibrium?
- Measure change in colour or colour intensity using colorimeter
- Use pH probe
- Measure electrical conductivity
- Titration- used when equilibrium is slow so that titration can be completed before there is much change in equilibrium mixture
What does mole fraction mean?
The amount of a given component in a given reaction mixture
Write equation used to calculate mole fraction
Mole fraction = number of moles of substance A/ total number of moles of all substances
What does partial pressure mean?
The pressure exerted by a single species in a reaction vessel
What is symbol of partial pressure?
P
Write equation to calculate partial pressure
Partial pressure = mole fraction x total pressure
What is relationship between concentration of a substance and its partial pressure?
Concentration of a substance is proportional to its partial pressure
What are the 3 common units of pressure used?
- Pascals
- Atmospheres
- Newtons per square metre
What type of brackets are used in Kc expressions?
Square brackets
What type of brackets are used in Kp expressions?
Round brackets
A reaction is represented by aA(g) + bB(g) = cC(g) + dD(g) calculate Kp for the system?
Kp= pC^c x pD^d / pA^a pB^b
Where pA = partial pressure of A
and a = number of moles of A
How do you calculate units for Kp?
Write out units for partial pressures in same arrangement as Kp equation and cancel out/ multiply together
Usually in Pa, kPa, atm etc. DO NOT CHANGE UNITS
What is symbol for equilibrium constant?
K
What does it mean when K is greater than 1?
Reaction favours product
What does it mean when K is less than 1?
Reaction favours reactants
What is effect of increasing temperature on K?
Equilibrium shifts to direction of endothermic reaction
What is effect of decreasing temperature on K?
Equilibrium shifts to direction of exothermic reaction
What is only factor affecting K?
Temperature
What is effect of increasing temperature on K for a forward endothermic reaction?
K increases as temperature increases
What is effect of increasing temperature on K for a forward exothermic reaction?
K decreases as temperature increases
What effect does catalyst have on K?
Catalysts does not affect position of equilibrium, they only have an effect on rate of reaction
