Chapter 11 Flashcards
What is Kc?
Kc is the equilibrium constant
What is the equilibrium constant calculated from?
The ratio of the product concentration compared to the reactant concentration
For the reaction H2 + I2 –> 2HI, what is the equation for the equilibrium constant?
kc = (HI squared) / (H2 X I2)
What does the definition of Kc only apply to?
Homogenous equilibria
What is a homogenous equilibria?
An equilibria where all the products and reactants are in the same phase
In a heterogenous equilibria, is everything included in the expression for Kc?
Not nececarily
What don’t you include in the expression for Kc?
Solids or liquids
Why don’t you include solids or liquids in the expression for Kc?
Because their concentrations stay constant throughout the reaction
When calculating the value of Kc, what are the concentrations?
The concentration at equilibrium
What will Fe2+ and Ag+ form an equilibrium with?
Fe3+ and Ag
How can you work out the equilibrium constant of a reaction between Fe2+ and Ag+ ions?
Titrate them, to calculate the equilibrium concentration of Fe2+ ions. From this you can calculate the equilibrium concentrations of the other components, and Kc
What do the square brackets represent in a Kc expression?
The square brackets represent the equilibrium concentrations
What do the powers represent in a Kc expression?
The powers represent the number of moles of each substance
What is the total pressure equal to?
The sum of the partial pressures
What is a mole fraction?
The proportion of a gas mixture that is a particular gas
What does the mole fraction of a gas in a mixture equal?
Number of moles in gas / Total Number of moles of gas in mixture
What does the partial pressure of a gas equal?
Mole fraction of gas X total pressure of mixture
What is Kp?
An equilibrium constant you can calculate when dealing with equilibria involving gases
What is the difference between Kp and Kc?
With Kp you deal with partial pressures
What is the unit of a partial pressure?
Atmosphere
When calculating Kp for heterogenous equilibria, what does the calulation only involve?
Gases
For a reaction where a solid S decomposes to form gases P and Q, what is the expression for Kp?
P(P)p(Q)
When a reversible reaction reaches a dynamic equilibrium, what happens?
The forward reaction happens at the same rate as the backward reaction
If you change the concentration, pressure or temperature of a reversible reaction, what are you going to do?
You are going to alter the position of the equilibrium
What is Le Chatelier’s principle?
If there’s a change in concentration, pressure or temperature, the equilibrium will move to help counteract the change
What does the greater the value of Kp or Kc mean?
The greater the value the further to the right the equilibrium lies
What does the smaller the value of Kp or Kc mean?
The smaller the value the further to the left the equilibrium lies
If the forward reaction is exothermic, and the temperature of the reaction is increased, what happens to the value of Kp?
The value of Kp decreases as there is less product
If the backward reaction is endothermic, why does the position of the equilibrium shift to the left when the temperature is raised?
The equilibrium shifts to the left to absorb the extra heat
As the value of the equilibrium constant is fixed at a given temperature, what happens if the concentration of one thing in the mixture changes?
The concentrations of the others must change to keep the value of Kc the same
What does increasing the total pressure do?
It increases the partial pressures of each of the products and reactants
Do catalysts effect the position of the equilibrium?
No, but they do mean an equilibrium can be reached faster
