Equilibria Flashcards
Give an example of a reversible reaction?
Carboxylic acid+ alcohol<> ester +water
What happens to the concentration of products and reactants as the reaction proceeds?
Product concentration increases and the reactant concentration decreases
When is equilibrium reached?
When the concentration of the reactants and products remains constant
What is a closed system?
One which is sealed
When is a reversible reaction said to be at dynamic equilibrium?
Rate of forward reaction= rate of reverse reaction
What are the 3 rules for dynamic equilibrium?
Concentrations of reactants and products remain constant
Concentrations are not usually equal
The reaction has not stopped
How can a reversible reaction’s equilibrium be altered ?
Altering the conditions of the reaction
What are the 3 things which can alter the equilibrium?
Concentration
Temperature
Total pressure
If a chemical system at equilibrium experiences a change in concentration, temperature or total pressure then what will the equilibrium do?
Shift to counter-act the imposed change
What are the 2 rules for equilibrium?
If equilibrium moves to the right ; more products are produced
If equilibrium moves to the left; more reactants will be produced
Where the equilibrium move to if there is an increase in concentration of any reactant?
Right
Where the equilibrium move to if there is an increase in concentration of any product?
Left
Where the equilibrium move to if there is an decrease in concentration of reactants?
Left
Where the equilibrium move to if there is an decrease in concentration of products?
Right
What happens if an alkali I.e OH- ions are added?
Br2+H2O<>2H+ + Br- + BrCl-
Br2 red
H+ colourless
The OH- ions of the alkali neutralise and remove the H+ ions of the acid. The equilibrium will shift to the right to replace the H+ ions. As a result the solution will appear colourless.
What happens if an acid I.e H+ ions are added?
Br2+H2O<>2H+ + Br- + BrCl-
Br2 red
H+ colourless
Adding an acid increases the H+ ion concentration. As a result the equilibrium shifts to the left to remove H+ ions and the solution will appear red
What is the enthalpy change for an exothermic reaction?
negative
What is the enthalpy change for an endothermic reaction?
positive
What effect does an increase in temperature have?
energy increases> positive value> ENDOTHERMIC
What does an increase in temperature do to the equilibrium?
equilibrium moves in ENDO- direction
What effect does a decrease in temperature have?
energy decreases>negative value> EXOTHERMIC
What does a decrease in temperature do to the equilibrium?
Equilibrium moves in EXO- direction
What is changes in pressure only important for?
reactions involving gases
What must you only look at when answering questions on the effect of changing pressure?
state symbols involving gases
What effect does increasing pressure have?
volume decreases, equilibrium moves to the side with the lowest volume, hence producing more of the molecules.
What effect does decreasing pressure have?
volume increases, equilibrium moves to side with largest volume, hence producing more of the molecules.
What effect would a change in pressure have if there is no overall decrease or increase in number of gaseous molecules i.e. same number of gaseous molecules on each side?
no effect
What do gases occupy much more than solids or liquids?
much more space
What will a catalyst increase the rate of ?
the rate of the forward and reverse reaction
As a catalyst increases the rate of the forward and reverse reaction, what happens to the dynamic equilibrium?
it will be achieved quicker
What effect does a catalyst have on the position of equilibrium?
NO EFFECT.
What are the laws of equilibrium used by and why?
industrial chemists to increase the yield of products
What is ammonia?
an important feedstock and can be used to make fertilisers, dyes, explosives and household cleaners
What is industry organised to make ?
as much profit as possible
What is the result of industries which are organised to make as much profit as possible?
reaction conditions are sometimes altered for economical reasons
What might it be inefficient to have a low temperature even if this favours more product to be produced?
The reaction may be too slow and not economical. Therefore a moderate temp is used.
What might it be inefficient to have high pressure even if this favours more product to be produced?
the equipment required for dealing with high pressure will be too expensive. Therefore, a moderate pressure will be used.
What happens to unreacted reactants and what will this favour?
recycled. produce more product.
What happens to the product(s)and what will this favour?
continuously removed. produce more product
What do many industrial processes use?
a catalyst
What does a catalyst not alter and what does it do?
the position of the equilibrium but does lower the quantity of energy required for the reaction.
What does using a catalyst also do?
speed up the reaction and makes the overall process more economical
