Chemical equilibrium summary

We've made it through 5 of the 8 chapters of Chem 102. Here is a summary of equilibrium, chapter15.

Next week we will start thermodynamics, Kevin will be in for demos on thusday for A04 and friday for A02.

Remember, midterm 2 on 13th March is approaching. If you still haven't gotten hold of a course pack yet it would be a good idea to get one.


Summary of chapter 15

We know chemical equilibrium has been reached when the concentrations no longer change with time
The equilibrium condition can be reached from either direction
The equilibrium constant of a reaction in the reverse direction is the inverse of the equilibrium constant of the reaction in the forward direction
The equilibrium constant of a reaction that has been multiplied by a number is the equilibrium constant of the reaction raised to a power equal to that number
The equilibrium constant for a net reaction made up of two or more steps is the product of the equilibrium constants for the individual steps
If K >> 1 (big) then equilibrium lies to the right (products)
If K << 1 (small) then equilibrium lies to the left (reactants)


Summary 2.
Leave solids and pure liquids out of equilibrium expressions, the concentration of these substances does not change with time.
Calculating Equilibrium Constants; is easy when we know all the equilibrium concentrations (or pressures), a balanced equation, and can write a rate expression. Don’t forget to convert to scientific notation.
When we know initial concentrations and an equilibrium concentration, use the stoichiometric coefficients to predict the change in concentrations.
Use the Initial, Change, Equilibrium (ICE) procedure to find all the equilibrium concentrations and sub these values into the equilibrium expression.


Comparing the magnitude of Q to Kc or Kp indicates the direction the reaction will shift to reach equilibrium


Calculating Equilibrium Concentrations; when we know K and all the initial concentrations only, use the ICE procedure and solve for x the change in concentration, possibly by solving a quadratic function.