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Chemistry revision Topic 4:Reversible reactions and Equilibria (Le…
Chemistry revision Topic 4:Reversible reactions and Equilibria
Reversible reactions are where the reactants can produce the products as well as the products can produce the reactants
⇌
shows the reaction can go in either direction
Dynamic Equilibria
Happens in a closed system
When the rate of the forward reaction=rate of the backward reaction
Doesn't mean the amounts of reactants and products are equal
If equilibrium lies on the left, the concentration of reactants is greater
Direction of reversible reactions can be altered by changing the reaction conditions
Pressure
Temperature
Concerntrations
Making ammonia
Nitrogen(air)+hydrogen(natural gas)<->ammonia
Conditions:
A pressure of 200 atmospheres
Iron catalyst
450°C temperature
Le Chatelier's Principle
If you change the conditions of a reversible reaction, the system will try to counteract the change
Pressure
Only affects when some reactants or products are gases
Raising
pressure favours reaction with less volume (
fewer gas molecules
)
Lowering
pressure favours reaction with more volume (
greater number of gas molecules
)
Temperature
Increase
temperature, equilibrium will favour
endothermic
direction: Yield of exothermic reaction will decrease,yield of endothermic reaction will increase
Decrease
temperature, equilibrium will favour
exothermic
direction: Yield of endothermic reaction will decrease, Yield of exothermic reaction will increase
Concentration
Increase
concentration of reactants, system
increases
concentration of products
Decrease
concentration of product, system
decreases
concentration of reactants