Equilibria Flashcards
What reaction studied in class is the Haber Process
Nitrogen + Hydrogen ⇌ ammonia
If you increase the temperature how will equilibrium be affected
It will favour the endothermic direction (backwards reaction)
If you decrease the temperature how will equilibrium be affected
It will favour the exothermic direction (forwards reaction)
If you increase the concentration how will equilibrium be affected
It will favour the direction that uses up the substance that has been added.
(If more products were added then it would favour the backwards reaction)
If you decrease the concentration how will equilibrium be affected
It will favour the direction that forms more of the substance that has been removed.
(If products were taken away then it would favour the forwards reaction)
If you increase the pressure how will equilibrium be affected
It will favour the direction that forms the fewest moles of gas.
(If there were more moles of gas in the products it would favour the forward reaction)
If you decrease the pressure how will equilibrium be affected
It will favour the direction that forms more gas molecules
(If there were more gas molecules in the products it would favour the backwards reaction)
What are reversible reactions
Where the products can react to reform the reactants
Both forward and backward reactions occur at the same time
What does this symbol mean: ΔH-
Exothermic reaction
What does this symbol mean: ΔH+
Endothermic reaction
What does exothermic mean
Energy is being released
What does endothermic mean
Energy is being taken in
When is the only time pressure can become a factor affecting equilibrium
If ALL elements are gaseous (g)
Dynamic equilibrium can only occur in a …
Closed system
(In an open system gases could escape so equilibrium would not be achieved)
What is dynamic equilibrium
The point at which there is the same amount of reactants as products
Why are the reaction conditions on an industrial scale controlled
To obtain an acceptable yield of product in an acceptable time
Why is a compromise temperature of 450 °C used to produce the best yield
Choosing a low temp would give the most yield however the reaction is too slow
Comprise of 450 °C is chosen so that it’s not too high that not enough yield is made but not too low that it takes to long to make
Why is a catalyst used in reversible reactions of an industrial scale
Increases rate of reaction, which often allows a lower temp to be used (saves energy & increases yield)
What catalyst is often used in reversible reactions on an industrial scale
Iron - cheap
Why would the yield be less than 100%
Incomplete reaction
Practical losses during experiment
Competing side reactions
What is a fuel cell
Uses continuous supply of a fuel.
Produces a voltage for as long as the fuel & oxygen are supplied (doesn’t go flat)
Fuel doesn’t burn but energy produced from the reaction is converted to electrical energy
Explain how a hydrogen fuel cell works
Hydrogen and oxygen react to produce a voltage
Water is the only product
What are the strengths of using a hydrogen - oxygen fuel cell
No moving parts
Quieter
Doesn’t need recharging
Clean (only product is water)
What are the weaknesses of using a hydrogen - oxygen fuel cell
Uses platinum electrodes - expensive
Hydrogen must be stored in the car
Hydrogen will run out and need replacing
Few hydrogen stations for refuelling
