Lecture 7 Flashcards
When do we use Kc?
When the equilibrium constant is defined in terms of concentrations
What can we use to quantify a system at equilibrium?
The equilibrium constant (Kc or Kp)
When do we used Kp?
When the equilibrium constant is defined in terms of pressure
If there the forward and reverse reactions are both occurring at equilibrium, what is happening to the species?
Their rates are identical so there is no net change in composition
Does it matter if an equilibrium reaction starts with the reactants or the products?
No the equilibrium composition will be the same regardless
What is c (degree sign circle)?
Standard concentration
= 1 molL -1
What is p (degree sign circle)?
Standard pressure
= 1 x 10^5 Pa
= 1 bar
What do standard pressure and concentration do?
Strip equilibrium of units
Makes it dimensionless
What does standard pressure and concentration mean for Kc and Kp?
We can simplify expressions for Kc but not Kp
When writing equilibrium constants, where do products and reactants go?
Products top
Reactants bottom
What is Dave’s Dogma?
Products raised to stoichiometric powers
Divided by reactants raised to theirs
Pure solids and pure liquids do not appear
What does the value of K give information about?
The extent of reaction at equilibrium
If the Kc is small where does the equilibrium lie?
Far to the left
When doing a concentration table when is it important to do a negative sign?
In the change in concentration row, the difference if it is less
If Kc is large where does the equilibrium lie?
To the right
When can you take the square root of both sides to find x?
When there is the same number of products as reactants ONLY
What is Q?
The reaction quotient
Identical form to K but can be used at any point of a reaction not just at equilibrium
Can Q have any value at a particular temp?
Yes
What is Le Chatelier’s principle?
If a system is disturbed, it will move in such a way to counteract the disturbance and restore equilibrium
What is the best way to do problems about responds to change?
A comparison of Q and K
Where does Q=K?
At equilibrium
How can we change the pressure?
By changing the volume or adding an inert gas
