Chemical Equilibria Flashcards
When is a system in equilibrium?
When the rate of the forward reaction is equal to the rate of the reverse reaction
When does a reaction system remain in equilibrium?
as long as the system is located (or closed)
What is a dynamic system?
one where reactants are being used up to form products and products are breaking down to form reactants but no change is observed in the reaction mixture; macroscopic properties (temperature and pressure) remain constant.
What is the position of equilibrium?
extent of a reaction when equilibrium is established
What are the features of a system at equilibrium?
-Rate of the forward reaction is equal to the rate of the backward reaction
-Concentration of reactants and products remains constant (*but is constantly moving)
-Systems are isolated
-Macroscopic properties remain constant (temp and pressure)
what are the two different types of equilibrium system?
Homogenous and Heterogeneous
What is heterogeneous equilibrium?
reactants and products are in different phases (states) (e.g. thermal decomposition) CaCO3(s)Heat⟶CaO (s)+CO2(g)
What is homogenous equilibrium?
reactants and products are in the same phase (state)
What is [A]?
concentration of chemical A in
moldm-3
What is Kc?
the equilibrium constant-product of the concentrations of products over the product of the concentrations of reactants gives a ratio and shows how far towards the right or left a reaction lies when a reaction is at equilibrium;
What are stoichiometric ratios used to give the the kc equations?
the power?
what type of equilibria doe kc deal
with?
homogeneous
what does the larger value for the Kc mean?
The more the reaction has gone to completion
what does a large kc greater than one mean?
products are “favoured”; equibrium lies towards the right.
what does a small Kc less than one mean?
reactants are “favoured”; equilibrium lies towards the left.
when will an equilibrium system only remain in equilibrium?
When it is isolated
What happens once the conditions of equilibrium are changed?
The system will no longer be in equilibrium
What are the conditions that affect equilibrium?
-temp
-pressure
-conc
What is Le Chatelier’s principal?
When a system under dynamic equilibrium is subjected to a change, the equilibrium will shift so as to oppose the change
what happens if the concentration of the reactants are increased? (in dynamic equilibrium)
They equilibrium shifts to the right hand side The yield of the product will increase
what happens when the concentration of products are decreased? (in dynamic equilibrium)
-The equilibrium shifts to the right hand side
-The yield of the product will increase
What are affected by change in pressure?
gases
what does an increase in pressure of an equilibrium mixture lead to?
the equilibrium moving so as to decrease the pressure.
-does this by decreasing the number of molecules. (Fewer moles = lower pressure so equilibrium shifts to the side with the least gas moles).
what does a decrease in pressure of the equilibrium mixture lead to?
the equilibrium mixture leads to the equilibrium moving so as to increase the pressure. It does this by increasing the number of molecules. (more moles = higher pressure so equilibrium shifts to the side with the most gas moles)
