Equilibria3.1.6.1 Flashcards
What are reversible reactions ?
Some reactions go to completion where the reactants are used up to form the products and the reaction stops when all of the reactants are used up
In reversible reactions the products can react to reform the original reactants
What is a closed system?
A closed system is one in which none of the reactants or products escape from the reaction mixture
Describe what happens in a dynamic equilibrium
In a dynamic equilibrium the reactants and products are dynamic (they are constantly moving)
In a dynamic equilibrium the rate of the forward reaction is the same as the rate of the backward reaction in a closed system, and the concentrations of the reactants and products is constant
What is an open system?
In an open system, matter and energy can be lost to the surroundings
What happens when a reaction takes place entirely in solution?
When a reaction takes place entirely in solution, equilibrium can be reached in open flasks as a negligible amount of material is lost through evaporation
If a reaction involves gases how can equilibrium be reached?
If the reaction involves gases, equilibrium can only be reached in a closed system
What does the position of the equilibrium refer to?
The position of the equilibrium refers to the relative amounts of products and reactants in an equilibrium mixture
What happens when the position of equilibrium shifts to the left?
When the position of equilibrium shifts to the left, it means the concentration of reactants increases
What happens to the position of equilibrium shifts to the right ?
When the position of equilibrium shifts to the right, it means the concentration of products increases
Define Le Chateliers principle?
Le Chatelier’s principle says that if a change is made to a system in dynamic equilibrium, the position of the equilibrium moves to counteract this change
What is this principle used to predict ?
The principle is used to predict changes to the position of equilibrium when there are changes in temperature, pressure or concentration
How does an increase in concentration affect equilibrium shifts for the haber process equation ?
Equilibrium shifts to the right to reduce the effect of increase in the concentration of a reactant
How does a decrease in concentration affect equilibrium shifts for the haber process equation?
Equilibrium shifts to the left to reduce the effect of the decrease in reactant (or an increase in the concentration of products)
When does pressure affect reactions ?
When products or reactants are gases
How does an increase in pressure affect equilibrium shift for the haber process equation?
Equilibrium shifts in the direction that produces the smaller number of molecules of gas to decrease the pressure again
How does a decrease in pressure affect the equilibrium for the haber process equation?
Equilibrium shifts in the direction that produces the larger molecules of gas to increase the pressure again
How does an increase in temperature affect equilibrium shifts for the haber process equation?
Equilibrium moves in the endothermic direction to reverse the change
How does a decrease in temperature affect equilibrium shifts for the haber process equation?
Equilibrium moves in the exothermic direction to reverse the change
What is a catalyst?
A catalyst is a substance that increases the rate of a chemical reaction (the increase the rate of the forward and reverse reaction equally)
What is the reason why catalyst cause a reaction?
Catalyst only causes a reaction to reach equilibrium faster
Do catalyst have an effect on the position of the equilibrium?
No catalysts do not have an effect on the position of the equilibrium once this is reached because they only caused a reaction to reach equilibrium
What catalyst is used in Haber process?
Iron catalyst
What are the actual conditions for the haber process?
450°C/725 Kelvin
200 atm
Iron catalyst
How does the industry compromise pressure conditions?
Compromise between yield and cost.
Higher pressure increase the yield but are expensive due to equipment cost.
Higher pressure, require stronger/more expensive reaction vessels
What are other strategies used in industry to maximise profit and yield in the production of ammonia?
Recycle are used nitrogen and hydrogen
Pass reactants over the catalyst quickly to avoid any equilibrium being reached. Ammonia is cooled and tapped off to remove it and drive direction forward
How does the industry compromise temperature conditions ?
Compromise between yield and rate.
Low temperatures increase the yield of ammonia, for the rate is too slow.
High temperature temperatures decrease the yield of ammonia, but increase the rate
Uses of ammonia
Fertiliser
Nylon
Drugs
Explosives
Dyes
Atom economy of the haber process reaction
100%
What state is ignored in the equilibrium constant expressions?
Solids
Look at mind map for notes
