AP Chem Semester 2 Final Flashcards
How do you find the rate for one component of a reaction from another?
You apply the stoichiometric coefficient
What is the sign of rate?
Rate is always positive
How can you find rate?
You can find it numerous ways depending on the problem
One way is using the change in concentration/change in time, but this only works if rate is constant.
If given a tangent line to the rate curve can you find the instantaneous rate?
Yes you can as the tangent line represents the slope at that point.
What is the reaction order of a molecule?
It is the exponent that decides it’s relationship to the rate. So for
Rate = [Product]^2 the rate order is 2.
How can you determine the reaction order of a substance experimentally?
Double the concentration of the substance, and see how the reaction rate changes.
What are the integrated rate laws for each common order and their corresponding half life formula?
All integrated rate laws take the form -kt + The first statement below.
Zero Order: [Concentration], [Concentration]/2k
First Order: ln([Concentration]), 0.693/k
Second Order: 1/[Concentration], 1/(k*[Concentration])
What is the Arrhenius equation and its constants/variables?
k = Ae^(-E/(R*T))
where A is the frequency factory, E is the activation energy, T is the temperature in Kelvin, and R is the ideal gas constant 8.314.
How can you determine the order of a reaction using a graph?
Look at the half life and see what order it aligns to
How do you find the rate law given the mechanisms if a mechanism which is not the first step is the RDS?
Assume equilibrium for previous steps and solve for the intermediate
How do you classify number of molecules of a given step?
1 reactant -> Unimolecular
2 reactants –> Bimolecular
3 reactants –> Termomolecular
What are the elements of the frequency factor?
Orientation factor p
Collision frequency z
A = p * z
What is an elementary step?
it is any step that composes an overall reaction that can not be broken down into more steps
What is the difference between heterogeneous and homogeneous catalysts?
Heterogeneous catalysts are in a different phase than the reactants, and homogeneous catalysts are in the same phase as the reactants
What is dynamic equilibrium?
The idea is that equilibrium is reached not because the products and reactants are no longer doing forward and backward reactions, but because the rate of the reactions is the exact same.
What is the law of mass action?
For a balanced equation aA + bB -> cC + dD
The equilibrium constant is
K = (C^cD^d)/(A^aB^b)
This is only true at equilibrium
What do different values of K mean?
High K means products aka forward reaction is favored, Low K means reactants aka reverse reaction is favored
What are the rules of K algebra when modifying equations?
If reversing an equation K_new = 1/K_old
If multiplying an equation by n K_new = K_old^n
If adding two equations together K_new = K_old1*K+old2
How do you convert from K_c to K_p?
K_p = K_c*(RT)^(c+d-a-b)
What is the assumed units of K_p
atm
What do you and don’t you include in an equilibrium expression?
Solids and Pure Liquids are not included, Gasses are and Aqueous solutions are
What is Q and how can you use it’s relationship to K to predict change in a system?
Q is the result of the law of mass action equation whenever the products and reactants are not at equilibrium (Note if there are not reactants q isn’t undefined it is infinity). This means Q can be gotten at any point, not just equilibrium.
If Q < K then the reaction will shift right
If Q > K then the reaction will shift left
If Q = K the reaction is at equilibrium
How do you find equilibrium with only the initial concentrations?
Use and ice table
What is a good method for simplifying a equilibrium problem and what is the tolerance for this method?
You can use an x is small approximation
x/(value it was supposed to be subtracted from ) * 100% should be less than 5% for this approximation to be valid