equilibria Flashcards
What does it mean that a reaction goes to completion?
The reaction continues until one of the reactants is completely used up and then stops
What happens if reversible reactions are carried out in a closed system?
Both forward and backwards reactions occur and a mixture of reactants and products is formed.
What is an equilibrium mixture?
A mixture in which all the components remain constant
What are the two features of a reaction at equilibrium?
Concentrations of reactants and products remain constant
Rate of forward and reverse reactions are equal
What is the yield of products and reactants if the position of equlibrium lie on the left?
mostly reactants, small yield of products
What is the yield of products and reactants if the position of equilibrium lies on the right?
very little reactants, high yield of products
What is a homogeneous system?
A system in which all the species present are in the same phase- either all liquid or all gas
What does dynamic equilibrium mean?
The reaction continues both forward and reverse, and the rate of both reactions are equal. This means concentrations of reactants and products remain equal
What is Le Chatelier’s principle?
An equilibrium moves to oppose any change imposed on it
What is the effect of a catalyst on position of equilibrium?
Do not affect the yield of chemical processes as they increase the rate of both the forward and reverse reaction by the same amount
What are the conditions of making ethanol and why is this a compromise?
Temperature of around 300ºC is used. Highest equilibrium yield will be obtained with a low temp, but the rate of reaction will be slow
Pressure of 6.5MPa is used. Higher pressure will increase yield, but is expensive
Acid H3PO4 is used as catalyst so equilibrium is reached quicker
What is Kc?
Measure of the position of equilibrium of a reaction
How do you calculate Kc?
[C]^c [D]^d ÷ [A]^a [B]^b
What does a very large value of Kc (>10^5) tell us?
Mainly product, very little reactant. Position of equilibrium is to the right
What does a very small value of Kc (<10^-5) tell us?
Mainly reactant, very little product. Position of equilibrium to the left
